Provided by: stress-ng_0.08.16-1_amd64 bug

NAME

       stress-ng - a tool to load and stress a computer system

SYNOPSIS

       stress-ng [OPTION [ARG]] ...

DESCRIPTION

       stress-ng  will  stress test a computer system in various selectable ways. It was designed
       to exercise various physical subsystems of a computer as well  as  the  various  operating
       system  kernel  interfaces.   stress-ng also has a wide range of CPU specific stress tests
       that exercise floating point, integer, bit manipulation and control flow.

       stress-ng was originally intended to make a machine work hard  and  trip  hardware  issues
       such as thermal overruns as well as operating system bugs that only occur when a system is
       being thrashed hard. Use stress-ng with caution as some of the tests can make a system run
       hot on poorly designed hardware and also can cause excessive system thrashing which may be
       difficult to stop.

       stress-ng can  also  measure  test  throughput  rates;  this  can  be  useful  to  observe
       performance  changes  across  different  operating  system  releases or types of hardware.
       However, it has never been intended to be used as a precise benchmark test  suite,  so  do
       NOT use it in this manner.

       Running stress-ng with root privileges will adjust out of memory settings on Linux systems
       to make the stressors unkillable in low memory situations, so use this judiciously.   With
       the  appropriate  privilege,  stress-ng can allow the ionice class and ionice levels to be
       adjusted, again, this should be used with care.

       One can specify the number of processes to invoke per type of stress  test;  specifying  a
       negative  or  zero  value  will  select  the  number of processors available as defined by
       sysconf(_SC_NPROCESSORS_CONF).

OPTIONS

       General stress-ng control options:

       --abort
              this option will force all running stressors to  abort  (terminate)  if  any  other
              stressor terminates prematurely because of a failure.

       --aggressive
              enables  more  file, cache and memory aggressive options. This may slow tests down,
              increase latencies and reduce the number of  bogo  ops  as  well  as  changing  the
              balance  of  user  time vs system time used depending on the type of stressor being
              used.

       -a N, --all N, --parallel N
              start N instances of all stressors in parallel. If N is less than  zero,  then  the
              number  of CPUs online is used for the number of instances.  If N is zero, then the
              number of CPUs in the system is used.

       -b N, --backoff N
              wait N microseconds between the start of each stress worker  process.  This  allows
              one to ramp up the stress tests over time.

       --class name
              specify the class of stressors to run. Stressors are classified into one or more of
              the following classes: cpu, cpu-cache, device, io, interrupt,  filesystem,  memory,
              network,  os, pipe, scheduler and vm.  Some stressors fall into just one class. For
              example the 'get' stressor is just in the 'os' class.  Other  stressors  fall  into
              more  than  one  class,  for  example, the 'lsearch' stressor falls into the 'cpu',
              'cpu-cache' and 'memory' classes as it exercises  all  these  three.   Selecting  a
              specific  class  will run all the stressors that fall into that class only when run
              with the --sequential option.

              Specifying a name followed by a question mark (for example --class vm?) will  print
              out all the stressors in that specific class.

       -n, --dry-run
              parse options, but do not run stress tests. A no-op.

       -h, --help
              show help.

       --ignite-cpu
              alter  kernel controls to try and maximize the CPU. This requires root privilege to
              alter various /sys interface controls.  Currently this only works for Intel P-State
              enabled x86 systems on Linux.

       --ionice-class class
              specify  ionice  class  (only  on  Linux).  Can  be idle (default), besteffort, be,
              realtime, rt.

       --ionice-level level
              specify ionice level (only on Linux). For idle, 0 is the only possible option.  For
              besteffort  or  realtime  values  0  (highest priority) to 7 (lowest priority). See
              ionice(1) for more details.

       --job jobfile
              run stressors using a jobfile.   The  jobfile  is  essentially  a  file  containing
              stress-ng options (without the leading --) with one option per line. Lines may have
              comments with comment text proceeded by the # character. A  simple  example  is  as
              follows:

              run sequential   # run stressors sequentially
              verbose          # verbose output
              metrics-brief    # show metrics at end of run
              timeout 60s      # stop each stressor after 60 seconds
              #
              # vm stressor options:
              #
              vm 2             # 2 vm stressors
              vm-bytes 128M    # 128MB available memory
              vm-keep          # keep vm mapping
              vm-populate      # populate memory
              #
              # memcpy stressor options:
              #
              memcpy 5         # 5 memcpy stressors

              The job file introduces the run command that specifies how to run the stressors:

              run sequential - run stressors sequentially
              run parallel - run stressors together in parallel

              Note that 'run parallel' is the default.

       -k, --keep-name
              by  default,  stress-ng  will  attempt  to  change the name of the stress processes
              according to their functionality; this option disables this and keeps  the  process
              names to be the name of the parent process, that is, stress-ng.

       --log-brief
              by  default stress-ng will report the name of the program, the message type and the
              process id as a prefix to all output. The --log-brief option will  output  messages
              without these fields to produce a less verbose output.

       --log-file filename
              write messages to the specified log file.

       --maximize
              overrides  the  default  stressor  settings  and  instead sets these to the maximum
              settings allowed.  These defaults can always be  overridden  by  the  per  stressor
              settings options if required.

       --metrics
              output  number of bogo operations in total performed by the stress processes.  Note
              that these are not a reliable metric of performance or throughput and have not been
              designed  to be used for benchmarking whatsoever. The metrics are just a useful way
              to observe how a system behaves when under various kinds of load.

              The following columns of information are output:

              Column Heading             Explanation
              bogo ops                   number of iterations of the  stressor  during  the  run.
                                         This  is  metric  of  how  much  overall "work" has been
                                         achieved in bogo operations.
              real time (secs)           average  wall  clock  duration  (in  seconds)   of   the
                                         stressor.  This  is the total wall clock time of all the
                                         instances of that particular  stressor  divided  by  the
                                         number of these stressors being run.
              usr time (secs)            total  user  time  (in seconds) consumed running all the
                                         instances of the stressor.
              sys time (secs)            total system time (in seconds) consumed running all  the
                                         instances of the stressor.
              bogo ops/s (real time)     total bogo operations per second based on wall clock run
                                         time. The wall clock  time  reflects  the  apparent  run
                                         time.  The  more processors one has on a system the more
                                         the work load can be distributed onto  these  and  hence
                                         the  wall  clock  time will reduce and the bogo ops rate
                                         will increase.  This is essentially the "apparent"  bogo
                                         ops rate of the system.
              bogo ops/s (usr+sys time)  total  bogo  operations  per  second based on cumulative
                                         user and system time.  This is the real bogo ops rate of
                                         the  system  taking  into  consideration the actual time
                                         execution  time  of  the   stressor   across   all   the
                                         processors.   Generally  this  will decrease as one adds
                                         more concurrent stressors due to  contention  on  cache,
                                         memory, execution units, buses and I/O devices.

       --metrics-brief
              enable metrics and only output metrics that are non-zero.

       --minimize
              overrides  the  default  stressor  settings  and  instead sets these to the minimum
              settings allowed.  These defaults can always be  overridden  by  the  per  stressor
              settings options if required.

       --no-madvise
              from  version  0.02.26  stress-ng automatically calls madvise(2) with random advise
              options before each mmap and munmap to stress the the vm subsystem a little harder.
              The --no-advise option turns this default off.

       --no-rand-seed
              Do  not seed the stress-ng psuedo-random number generator with a quasi random start
              seed, but instead seed it with constant values. This forces tests to run each  time
              using the same start conditions which can be useful when one requires reproduceable
              stress tests.

       --oomable
              Do not respawn a stressor if it gets killed by the Out-of-Memory (OOM) killer.  The
              default  behaviour  is  to  restart  a new instance of a stressor if the kernel OOM
              killer terminates the process. This option disables this default behaviour.

       --page-in
              touch allocated pages that are not in core, forcing them to be paged back in.  This
              is  a  useful option to force all the allocated pages to be paged in when using the
              bigheap, mmap and vm stressors.  It will  severely  degrade  performance  when  the
              memory in the system is less than the allocated buffer sizes.  This uses mincore(2)
              to determine the pages that are not in core and hence need touching  to  page  them
              back in.

       --pathological
              enable  stressors  that  are  known  to  hang  systems.  Some stressors can quickly
              consume resources in such a way that they can rapidly  hang  a  system  before  the
              kernel  can  OOM kill them. These stressors are not enabled by default, this option
              enables them, but you probably don't want to do this. You have been warned.

       --perf measure processor and system activity using perf  events.  Linux  only  and  caveat
              emptor, according to perf_event_open(2): "Always double-check your results! Various
              generalized events have had wrong values.".  Note that with Linux 4.7 one needs  to
              have   CAP_SYS_ADMIN   capabilities   for   this   option   to   work,   or  adjust
              /proc/sys/kernel/perf_event_paranoid to below 2 to use this without CAP_SYS_ADMIN.

       -q, --quiet
              do not show any output.

       -r N, --random N
              start N random stress workers. If N is 0, then the number of configured  processors
              is used for N.

       --sched scheduler
              select the named scheduler (only on Linux). To see the list of available schedulers
              use: stress-ng --sched which

       --sched-prio prio
              select the scheduler priority level (only on Linux).  If  the  scheduler  does  not
              support this then the default priority level of 0 is chosen.

       --sequential N
              sequentially  run  all  the  stressors  one by one for a default of 60 seconds. The
              number of instances of each of the individual stressors to be started is N.   If  N
              is  less  than  zero,  then  the  number  of  CPUs online is used for the number of
              instances.  If N is zero, then the number of CPUs in the system is used.   Use  the
              --timeout option to specify the duration to run each stressor.

       --stressors
              output the names of the available stressors.

       --syslog
              log output (except for verbose -v messages) to the syslog.

       --taskset list
              set CPU affinity based on the list of CPUs provided; stress-ng is bound to just use
              these CPUs (Linux only). The CPUs to be used are specified  by  a  comma  separated
              list  of  CPU  (0  to N-1). One can specify a range of CPUs using '-', for example:
              --taskset 0,2-3,6,7-11

       --temp-path path
              specify a path for stress-ng temporary directories and temporary files; the default
              path  is  the current working directory.  This path must have read and write access
              for the stress-ng stress processes.

       --thrash
              This can only be used when running on Linux and with root  privilege.  This  option
              starts  a  background  thrasher  process  that works through all the processes on a
              system and tries to page as many pages in the processes  as  possible.   This  will
              cause considerable amount of thrashing of swap on an over-committed system.

       -t N, --timeout T
              stop  stress  test  after  T  seconds.  One  can  also specify the units of time in
              seconds, minutes, hours, days or years with the suffix s, m, h, d or  y.   Note:  A
              timeout of 0 will run stress-ng without any timeouts (run forever).

       --timer-slack N
              adjust  the  per  process timer slack to N nanoseconds (Linux only). Increasing the
              timer slack allows the kernel to coalesce timer events by adding some fuzzinesss to
              timer  expiration times and hence reduce wakeups.  Conversely, decreasing the timer
              slack will increase wakeups.  A value of 0 for the timer-slack will set the  system
              default of 50,000 nanoseconds.

       --times
              show  the cumulative user and system times of all the child processes at the end of
              the stress run.  The percentage of  utilisation  of  available  CPU  time  is  also
              calculated from the number of on-line CPUs in the system.

       --tz   collect  temperatures from the available thermal zones on the machine (Linux only).
              Some devices may have one or more thermal zones, where as others may have none.

       -v, --verbose
              show all debug, warnings and normal information output.

       --verify
              verify results when a test is run. This is not available on all  tests.  This  will
              sanity  check  the  computations  or  memory contents from a test run and report to
              stderr any unexpected failures.

       -V, --version
              show version.

       -x, --exclude list
              specify a list of one or more stressors to exclude (that  is,  do  not  run  them).
              This is useful to exclude specific stressors when one selects many stressors to run
              using the --class option, --sequential, --all and --random  options.  Example,  run
              the cpu class stressors concurrently and exclude the numa and search stressors:

              stress-ng --class cpu --all 1 -x numa,bsearch,hsearch,lsearch

       -Y, --yaml filename
              output gathered statistics to a YAML formatted file named 'filename'.

       Stressor specific options:

       --affinity N
              start N workers that rapidly change CPU affinity (only on Linux). Rapidly switching
              CPU affinity can contribute to poor cache behaviour.

       --affinity-ops N
              stop affinity workers after N bogo affinity operations (only on Linux).

       --affinity-rand
              switch CPU affinity randomly rather than the default of sequentially.

       --af-alg N
              start N workers that exercise the AF_ALG socket domain by  hashing  and  encrypting
              various  sized  random  messages.  This exercises the SHA1, SHA224, SHA256, SHA384,
              SHA512, MD4, MD5, RMD128, RMD160, RMD256,  RMD320,  WP256,  WP384,  WP512,  TGR128,
              TGR160,   TGR192   hashes  and  the  cbc(aes),  lrw(aes),  ofb(aes),  xts(twofish),
              xts(serpent), xts(cast6), xts(camellia), lrw(twofish),  lrw(cast6),  lrw(camellia),
              salsa20 skcipers.

       --af-alg-ops N
              stop af-alg workers after N AF_ALG messages are hashed.

       --aio N
              start  N  workers  that issue multiple small asynchronous I/O writes and reads on a
              relatively small temporary file using the POSIX aio interface.  This will just  hit
              the  file  system  cache  and  soak up a lot of user and kernel time in issuing and
              handling I/O requests.  By default, each worker process will handle  16  concurrent
              I/O requests.

       --aio-ops N
              stop POSIX asynchronous I/O workers after N bogo asynchronous I/O requests.

       --aio-requests N
              specify the number of POSIX asynchronous I/O requests each worker should issue, the
              default is 16; 1 to 4096 are allowed.

       --aiol N
              start N workers that issue multiple 4K random asynchronous  I/O  writes  using  the
              Linux   aio   system   calls   io_setup(2),   io_submit(2),   io_getevents(2)   and
              io_destroy(2).  By default, each worker  process  will  handle  16  concurrent  I/O
              requests.

       --aiol-ops N
              stop Linux asynchronous I/O workers after N bogo asynchronous I/O requests.

       --aiol-requests N
              specify the number of Linux asynchronous I/O requests each worker should issue, the
              default is 16; 1 to 4096 are allowed.

       --apparmor N
              start N workers that exercise various parts of the  AppArmor  interface.  Currently
              one  needs root permission to run this particular test. This test is only available
              on Linux systems with AppArmor support.

       --apparmor-ops
              stop the AppArmor workers after N bogo operations.

       --atomic N
              start N workers that exercise various GCC __atomic_*() built in  operations  on  8,
              16,  32  and  64 bit integers that are shared among the N workers. This stressor is
              only available for builds using GCC 4.7.4 or higher. The stressor forces many front
              end cache stalls and cache references.

       --atomic-ops N
              stop the atomic workers after N bogo atomic operations.

       -B N, --bigheap N
              start  N workers that grow their heaps by reallocating memory. If the out of memory
              killer (OOM) on Linux kills the worker or the allocation fails then the  allocating
              process  starts all over again.  Note that the OOM adjustment for the worker is set
              so that the OOM killer will treat these workers as the first candidate processes to
              kill.

       --bigheap-ops N
              stop the big heap workers after N bogo allocation operations are completed.

       --bigheap-growth N
              specify  amount  of  memory  to  grow heap by per iteration. Size can be from 4K to
              64MB. Default is 64K.

       --bind-mount N
              start N workers that repeatedly bind mount / to / inside a user namespace. This can
              consume  resources  rapidly,  forcing  out  of  memory  situations. Do not use this
              stressor unless you want to risk hanging your machine.

       --bind-mount-ops N
              stop after N bind mount bogo operations.

       --branch N
              start N workers that randomly jump to 256 randomly  selected  locations  and  hence
              exercise the CPU branch prediction logic.

       --branch-ops N
              stop the branch stressors after N jumps

       --brk N
              start  N  workers  that  grow the data segment by one page at a time using multiple
              brk(2) calls. Each successfully allocated new page  is  touched  to  ensure  it  is
              resident  in memory.  If an out of memory condition occurs then the test will reset
              the data segment to the point  before  it  started  and  repeat  the  data  segment
              resizing  over again.  The process adjusts the out of memory setting so that it may
              be killed by the out of memory (OOM) killer  before  other  processes.   If  it  is
              killed  by  the OOM killer then it will be automatically re-started by a monitoring
              parent process.

       --brk-ops N
              stop the brk workers after N bogo brk operations.

       --brk-notouch
              do not touch each newly allocated data segment page. This disables the  default  of
              touching  each  newly  allocated  page and hence avoids the kernel from necessarily
              backing the page with real physical memory.

       --bsearch N
              start N workers that binary  search  a  sorted  array  of  32  bit  integers  using
              bsearch(3).  By  default,  there are 65536 elements in the array.  This is a useful
              method to exercise random access of memory and processor cache.

       --bsearch-ops N
              stop the bsearch worker after N bogo bsearch operations are completed.

       --bsearch-size N
              specify the size (number of 32 bit integers) in the array to bsearch. Size  can  be
              from 1K to 4M.

       -C N, --cache N
              start  N  workers  that perform random wide spread memory read and writes to thrash
              the  CPU  cache.   The  code  does  not  intelligently  determine  the  CPU   cache
              configuration  and  so  it  may  be  sub-optimal  in  producing hit-miss read/write
              activity for some processors.

       --cache-fence
              force write serialization on each store operation (x86 only). This is a  no-op  for
              non-x86 architectures.

       --cache-flush
              force  flush  cache on each store operation (x86 only). This is a no-op for non-x86
              architectures.

       --cache-level N
              specify level of cache to exercise (1=L1 cache, 2=L2  cache,  3=L3/LLC  cache  (the
              default)).   If  the  cache  hierarchy cannot be determined, built-in defaults will
              apply.

       --cache-no-affinity
              do not change processor affinity when --cache is in effect.

       --cache-ops N
              stop cache thrash workers after N bogo cache thrash operations.

       --cache-prefetch
              force read prefetch on next read address on architectures that support prefetching.

       --cache-ways N
              specify the number of cache ways to exercise. This allows a subset of  the  overall
              cache size to be exercised.

       --cap N
              start  N  workers that read per process capabililties via calls to capget(2) (Linux
              only).

       --cap-ops N
              stop after N cap bogo operations.

       --chdir N
              start N workers that change directory between directories using chdir(2).

       --chdir-ops N
              stop after N chdir bogo operations.

       --chdir-dirs N
              exercise chdir on N directories. The default is 8192 directories, this allows 64 to
              65536 directories to be used instead.

       --chmod N
              start  N  workers  that change the file mode bits via chmod(2) and fchmod(2) on the
              same file. The greater the value for N then the more contention on the single file.
              The stressor will work through all the combination of mode bits.

       --chmod-ops N
              stop after N chmod bogo operations.

       --chown N
              start  N workers that exercise chown(2) on the same file. The greater the value for
              N then the more contention on the single file.

       --chown-ops N
              stop the chown workers after N bogo chown(2) operations.

       --chroot N
              start N workers that exercise chroot(2) on various valid and invalid chroot  paths.
              (Linux only).

       --chroot-ops N
              stop the chroot workers after N bogo chroot(2) operations.

       --clock N
              start  N workers exercising clocks and POSIX timers. For all known clock types this
              will exercise clock_getres(2), clock_gettime(2) and  clock_nanosleep(2).   For  all
              known  timers  it  will create a 50000ns timer and busy poll this until it expires.
              This stressor will cause frequent context switching.

       --clock-ops N
              stop clock stress workers after N bogo operations.

       --clone N
              start N workers that create clones  (via  the  clone(2)  system  call).  This  will
              rapidly  try  to create a default of 8192 clones that immediately die and wait in a
              zombie state until they are reaped.  Once the maximum number of clones  is  reached
              (or  clone  fails  because  one  has  reached the maximum allowed) the oldest clone
              thread is reaped and a new clone is then created in a  first-in  first-out  manner,
              and  then  repeated.   A  random  clone  flag  is selected for each clone to try to
              exercise different clone operarions.  The clone stressor is a Linux only option.

       --clone-ops N
              stop clone stress workers after N bogo clone operations.

       --clone-max N
              try to create as many as N clone threads. This may not be  reached  if  the  system
              limit is less than N.

       --context N
              start  N  workers  that  run three threads that use swapcontext(3) to implement the
              thread-to-thread context switching. This exercises rapid process context saving and
              restoring and is bandwidth limited by register and memory save and restore rates.

       --context-ops N
              stop  N context workers after N bogo context switches.  In this stressor, 1 bogo op
              is equivalent to 1000 swapcontext calls.

       --copy-file N
              start N stressors that copy a file using the Linux copy_file_range(2) system  call.
              2MB  chunks  of  data  are  copyied  from  random locations from one file to random
              locations to a destination file.  By default, the files are 256 MB in size. Data is
              sync'd to the filesystem after each copy_file_range(2) call.

       --copy-file-ops N
              stop after N copy_file_range() calls.

       --copy-file-bytes N
              copy  file size, the default is 256 MB. One can specify the size as % of free space
              on the file system or in units of Bytes, KBytes, MBytes and GBytes using the suffix
              b, k, m or g.

       -c N, --cpu N
              start  N  workers  exercising  the  CPU  by  sequentially  working  through all the
              different CPU stress methods. Instead of exercising all the CPU stress methods, one
              can specify a specific CPU stress method with the --cpu-method option.

       --cpu-ops N
              stop cpu stress workers after N bogo operations.

       -l P, --cpu-load P
              load  CPU  with  P  percent  loading for the CPU stress workers. 0 is effectively a
              sleep (no load) and 100 is full loading.  The loading loop is broken  into  compute
              time (load%) and sleep time (100% - load%). Accuracy depends on the overall load of
              the processor and the responsiveness of the scheduler, so the actual  load  may  be
              different  from  the desired load.  Note that the number of bogo CPU operations may
              not be linearly scaled with the load as some systems employ CPU  frequency  scaling
              and  so  heavier  loads  produce  an  increased  CPU frequency and greater CPU bogo
              operations.

              Note: This option only applies to the --cpu stressor option and not to all  of  the
              cpu class of stressors.

       --cpu-load-slice S
              note  -  this option is only useful when --cpu-load is less than 100%. The CPU load
              is broken into multiple busy and idle  cycles.  Use  this  option  to  specify  the
              duration  of  a  busy  time  slice.  A negative value for S specifies the number of
              iterations to run before idling the CPU (e.g. -30 invokes 30 iterations  of  a  CPU
              stress  loop).   A zero value selects a random busy time between 0 and 0.5 seconds.
              A positive value for S specifies the number of milliseconds to  run  before  idling
              the CPU (e.g. 100 keeps the CPU busy for 0.1 seconds).  Specifying small values for
              S lends to small time slices and smoother  scheduling.   Setting  --cpu-load  as  a
              relatively  low  value  and --cpu-load-slice to be large will cycle the CPU between
              long idle and busy cycles and exercise  different  CPU  frequencies.   The  thermal
              range  of  the  CPU  is  also  cycled,  so this is a good mechanism to exercise the
              scheduler, frequency scaling and passive/active thermal cooling mechanisms.

              Note: This option only applies to the --cpu stressor option and not to all  of  the
              cpu class of stressors.

       --cpu-method method
              specify  a  cpu  stress  method.  By  default, all the stress methods are exercised
              sequentially, however one can specify just one  method  to  be  used  if  required.
              Available cpu stress methods are described as follows:

              Method           Description
              all              iterate over all the below cpu stress methods
              ackermann        Ackermann function: compute A(3, 10), where:
                                A(m, n) = n + 1 if m = 0;
                                A(m - 1, 1) if m > 0 and n = 0;
                                A(m - 1, A(m, n - 1)) if m > 0 and n > 0
              bitops           various  bit operations from bithack, namely: reverse bits, parity
                               check, bit count, round to nearest power of 2
              callfunc         recursively call 8 argument C function to a depth  of  1024  calls
                               and unwind

              cfloat           1000 iterations of a mix of floating point complex operations
              cdouble          1000  iterations  of  a  mix  of  double  floating  point  complex
                               operations
              clongdouble      1000 iterations of a mix of long  double  floating  point  complex
                               operations
              correlate        perform a 16384 × 1024 correlation of random doubles
              crc16            compute 1024 rounds of CCITT CRC16 on random data
              decimal32        1000  iterations  of  a  mix  of  32  bit  decimal  floating point
                               operations (GCC only)
              decimal64        1000 iterations  of  a  mix  of  64  bit  decimal  floating  point
                               operations (GCC only)
              decimal128       1000  iterations  of  a  mix  of  128  bit  decimal floating point
                               operations (GCC only)
              dither           Floyd–Steinberg dithering of a 1024 × 768 random image from 8 bits
                               down to 1 bit of depth.
              djb2a            128  rounds  of  hash  DJB2a  (Dan  Bernstein  hash  using the xor
                               variant) on 128 to 1 bytes of random strings
              double           1000 iterations of  a  mix  of  double  precision  floating  point
                               operations
              euler            compute e using n = (1 + (1 ÷ n)) ↑ n
              explog           iterate on n = exp(log(n) ÷ 1.00002)
              factorial        find  factorials  from  1..150  using  Stirling's  and Ramanujan's
                               approximations
              fibonacci        compute Fibonacci sequence of 0, 1, 1, 2, 5, 8...
              fft              4096 sample Fast Fourier Transform
              float            1000 iterations of a mix of floating point operations
              fnv1a            128 rounds of hash FNV-1a (Fowler–Noll–Vo hash using the xor  then
                               multiply variant) on 128 to 1 bytes of random strings
              gamma            calculate  the  Euler-Mascheroni  constant  γ  using  the limiting
                               difference between the harmonic series (1 + 1/2 + 1/3 + 1/4 +  1/5
                               ... + 1/n) and the natural logarithm ln(n), for n = 80000.
              gcd              compute GCD of integers
              gray             calculate  binary  to  gray  code and gray code back to binary for
                               integers from 0 to 65535
              hamming          compute Hamming H(8,4) codes on 262144 lots of 4  bit  data.  This
                               turns 4 bit data into 8 bit Hamming code containing 4 parity bits.
                               For data bits d1..d4, parity bits are computed as:
                                 p1 = d2 + d3 + d4
                                 p2 = d1 + d3 + d4
                                 p3 = d1 + d2 + d4
                                 p4 = d1 + d2 + d3
              hanoi            solve a 21 disc Towers of Hanoi stack using the recursive solution
              hyperbolic       compute sinh(θ) × cosh(θ) + sinh(2θ) + cosh(3θ) for float,  double
                               and  long  double hyperbolic sine and cosine functions where θ = 0
                               to 2π in 1500 steps
              idct             8 × 8 IDCT (Inverse Discrete Cosine Transform)
              int8             1000 iterations of a mix of 8 bit integer operations
              int16            1000 iterations of a mix of 16 bit integer operations
              int32            1000 iterations of a mix of 32 bit integer operations
              int64            1000 iterations of a mix of 64 bit integer operations
              int128           1000 iterations of a mix of 128 bit integer operations (GCC only)
              int32float       1000 iterations of a mix of 32  bit  integer  and  floating  point
                               operations
              int32double      1000  iterations  of  a mix of 32 bit integer and double precision
                               floating point operations
              int32longdouble  1000 iterations of a  mix  of  32  bit  integer  and  long  double
                               precision floating point operations
              int64float       1000  iterations  of  a  mix  of 64 bit integer and floating point
                               operations
              int64double      1000 iterations of a mix of 64 bit integer  and  double  precision
                               floating point operations
              int64longdouble  1000  iterations  of  a  mix  of  64  bit  integer and long double
                               precision floating point operations
              int128float      1000 iterations of a mix of 128 bit  integer  and  floating  point
                               operations (GCC only)
              int128double     1000  iterations  of a mix of 128 bit integer and double precision
                               floating point operations (GCC only)

              int128longdouble 1000 iterations of a mix  of  128  bit  integer  and  long  double
                               precision floating point operations (GCC only)
              int128decimal32  1000  iterations  of  a  mix of 128 bit integer and 32 bit decimal
                               floating point operations (GCC only)
              int128decimal64  1000 iterations of a mix of 128 bit integer  and  64  bit  decimal
                               floating point operations (GCC only)
              int128decimal128 1000  iterations  of  a mix of 128 bit integer and 128 bit decimal
                               floating point operations (GCC only)
              jenkin           Jenkin's integer hash on 128 rounds of 128..1 bytes of random data
              jmp              Simple unoptimised compare >, <, == and jmp branching
              ln2              compute ln(2) based on series:
                                1 - 1/2 + 1/3 - 1/4 + 1/5 - 1/6 ...
              longdouble       1000 iterations of a mix of long double precision  floating  point
                               operations
              loop             simple empty loop
              matrixprod       matrix product of two 128 × 128 matrices of double floats. Testing
                               on 64 bit x86 hardware shows that this is provides a good  mix  of
                               memory,  cache  and  floating point operations and is probably the
                               best CPU method to use to make a CPU run hot.
              nsqrt            compute sqrt() of long doubles using Newton-Raphson
              omega            compute the omega constant defined by Ωe↑Ω  =  1  using  efficient
                               iteration of Ωn+1 = (1 + Ωn) / (1 + e↑Ωn)
              parity           compute  parity  using  various  methods  from  the  Standford Bit
                               Twiddling Hacks.  Methods employed are: the naïve way,  the  naïve
                               way  with  the  Brian  Kernigan  bit  counting  optimisation,  the
                               multiply way, the parallel way,  and  the  lookup  table  ways  (2
                               variations).
              phi              compute the Golden Ratio ϕ using series
              pi               compute π using the Srinivasa Ramanujan fast convergence algorithm
              pjw              128  rounds  of  hash  pjw  function  on  128 to 1 bytes of random
                               strings
              prime            find all the primes in the  range   1..1000000  using  a  slightly
                               optimised brute force naïve trial division search
              psi              compute ψ (the reciprocal Fibonacci constant) using the sum of the
                               reciprocals of the Fibonacci numbers
              queens           compute all the solutions of the  classic  8  queens  problem  for
                               board sizes 1..12
              rand             16384  iterations  of  rand(), where rand is the MWC pseudo random
                               number generator.  The MWC random function concatenates two 16 bit
                               multiply-with-carry generators:
                                x(n) = 36969 × x(n - 1) + carry,
                                y(n) = 18000 × y(n - 1) + carry mod 2 ↑ 16

                               and has period of around 2 ↑ 60
              rand48           16384 iterations of drand48(3) and lrand48(3)
              rgb              convert RGB to YUV and back to RGB (CCIR 601)
              sdbm             128 rounds of hash sdbm (as used in the SDBM database and GNU awk)
                               on 128 to 1 bytes of random strings
              sieve            find the primes in  the  range  1..10000000  using  the  sieve  of
                               Eratosthenes
              sqrt             compute  sqrt(rand()),  where rand is the MWC pseudo random number
                               generator
              trig             compute sin(θ) × cos(θ) + sin(2θ) + cos(3θ) for float, double  and
                               long  double  sine  and cosine functions where θ = 0 to 2π in 1500
                               steps
              union            perform integer arithmetic on a mix of bit fields in  a  C  union.
                               This  exercises  how well the compiler and CPU can perform integer
                               bit field loads and stores.
              zeta             compute the Riemann Zeta function ζ(s) for s = 2.0..10.0

              Note that some of these methods try to exercise the CPU with computations found  in
              some  real  world  use  cases.  However,  the code has not been optimised on a per-
              architecture basis, so may be a sub-optimal compared to hand-optimised code used in
              some applications.  They do try to represent the typical instruction mixes found in
              these use cases.

       --cpu-online N
              start N workers that put randomly selected CPUs offline and online. This Linux only
              stressor requires root privilege to perform this action.

       --cpu-online-ops N
              stop after offline/online operations.

       --crypt N
              start  N  workers  that encrypt a 16 character random password using crypt(3).  The
              password is encrypted using MD5, SHA-256 and SHA-512 encryption methods.

       --crypt-ops N
              stop after N bogo encryption operations.

       --cyclic N
              start N workers that exercise the real time FIFO or  Round  Robin  schedulers  with
              cyclic  nanosecond  sleeps. Normally one would just use 1 worker instance with this
              stressor to get reliable statistics.  This stressor measures the first 10  thousand
              latencies  and  calculates  the  mean,  mode, minimum, maximum latencies along with
              various latency percentiles for the just the first cyclic  stressor  instance.  One
              has  to  run this stressor as root to enable the real time scheduling policies. The
              FIFO scheduling policy is the default.

       --cyclic-ops N
              stop after N sleeps.

       --cyclic-dist N
              calculate and print a latency distribution with  the  interval  of  N  nanoseconds.
              This is helpful to see where the latencies are clustering.

       --cyclic-method [ clock_ns | itimer | poll | posix_ns ]
              specify the cyclic method to be used. The available cyclic methods are as follows:

              Method           Description
              clock_ns         sleep  for  the  specified  time using the clock_nanosleep(2) high
                               resolution nanosleep and the CLOCK_REALTIME real time clock.
              itimer           wakeup a paused process with a CLOCK_REALTIME itimer signal.
              poll             delay for the specified time using a poll delay loop  that  checks
                               for  time  changes  using  clock_gettime(2)  on the CLOCK_REALTIME
                               clock.
              posix_ns         sleep for the specified time using  the  POSIX  nanosleep(2)  high
                               resolution nanosleep.
              pselect          sleep  for  the  specified  time  using  pselect(2) with null file
                               descriptors.

       --cyclic-policy [ fifo | rr ]
              specify the desired real time scheduling policy, ff  (first-in,  first-out)  or  rr
              (round robin).

       --cyclic-prio P
              specify the scheduling priority P. Range from 1 (lowest) to 100 (highest).

       --cyclic-sleep N
              sleep   for  N  nanoseconds  per  test  cycle  using  clock_nanosleep(2)  with  the
              CLOCK_REALTIME timer. Range from 1 to 1000000000 nanoseconds.

       --daemon N
              start N workers that each create a daemon  that  dies  immediately  after  creating
              another  daemon  and  so  on. This effectively works through the process table with
              short lived processes that do not have a parent and are waited for by  init.   This
              puts  pressure on init to do rapid child reaping.  The daemon processes perform the
              usual mix of calls to turn into typical UNIX daemons, so this  artificially  mimics
              very heavy daemon system stress.

       --daemon-ops N
              stop daemon workers after N daemons have been created.

       --dccp N
              start  N  workers  that send and receive data using the Datagram Congestion Control
              Protocol  (DCCP)  (RFC4340).  This  involves  a  pair  of  client/server  processes
              performing rapid connect, send and receives and disconnects on the local host.

       --dccp-domain D
              specify  the  domain  to  use,  the  default  is  ipv4. Currently ipv4 and ipv6 are
              supported.

       --dccp-port P
              start DCCP at port P. For N dccp worker processes, ports P to P - 1 are used.

       --dccp-ops N
              stop dccp stress workers after N bogo operations.

       --dccp-opts [ send | sendmsg | sendmmsg ]
              by default, messages are sent using send(2). This option allows one to specify  the
              sending  method  using  send(2),  sendmsg(2) or sendmmsg(2).  Note that sendmmsg is
              only available for Linux systems that support this system call.

       -D N, --dentry N
              start N workers that create and remove directory entries.  This should create  file
              system  meta  data  activity. The directory entry names are suffixed by a gray-code
              encoded number to try to mix up the hashing of the namespace.

       --dentry-ops N
              stop denty thrash workers after N bogo dentry operations.

       --dentry-order [ forward | reverse | stride | random ]
              specify unlink order of dentries, can be one of forward, reverse, stride or random.
              By  default,  dentries are unlinked in random order.  The forward order will unlink
              them from first to last, reverse order will unlink them from last to first,  stride
              order  will  unlink  them  by  stepping  around order in a quasi-random pattern and
              random order will randomly select one of forward, reverse or stride orders.

       --dentries N
              create N dentries per dentry thrashing loop, default is 2048.

       --dev N
              start N workers that exercise the /dev  devices.  Each  worker  runs  5  concurrent
              threads  that  perform  open(2),  fstat(2),  lseek(2),  poll(2), fcntl(2), mmap(2),
              munmap(2), fsync(2) and close(2) on each device.  Note that  watchdog  devices  are
              not exercised.

       --dev-ops N
              stop dev workers after N bogo device exercising operations.

       --dir N
              start N workers that create and remove directories using mkdir and rmdir.

       --dir-ops N
              stop directory thrash workers after N bogo directory operations.

       --dir-dirs N
              exercise  dir  on N directories. The default is 8192 directories, this allows 64 to
              65536 directories to be used instead.

       --dirdeep N
              start N workers that create a depth-first tree of directories to a maximum depth as
              limited  by  PATH_MAX  or ENAMETOOLONG (which ever occurs first).  By default, each
              level of the tree contains one directory, but this can be increased to a maximum of
              10  sub-trees  using the --dirdeep-dir option.  To stress inode creation, a symlink
              and a hardlink to a file at the root of the tree is created in each level.

       --dirdeep-ops N
              stop directory depth workers after N bogo directory operations.

       --dirdeep-dirs N
              create N directories at each tree level. The default is just 1 but can be increased
              to a maximum of 10 per level.

       --dirdeep-inodes N
              consume  up  to N inodes per dirdeep stressor while creating directories and links.
              The value N can be the number of inodes or a percentage of the total available free
              inodes on the filesystem being used.

       --dnotify N
              start   N  workers  performing  file  system  activities  such  as  making/deleting
              files/directories, renaming files, etc. to  stress  exercise  the  various  dnotify
              events (Linux only).

       --dnotify-ops N
              stop inotify stress workers after N dnotify bogo operations.

       --dup N
              start N workers that perform dup(2) and then close(2) operations on /dev/zero.  The
              maximum opens at one time is system defined, so  the  test  will  run  up  to  this
              maximum, or 65536 open file descriptors, which ever comes first.

       --dup-ops N
              stop the dup stress workers after N bogo open operations.

       --epoll N
              start  N  workers  that  perform  various  related  socket  stress  activity  using
              epoll_wait(2) to monitor and handle new connections.  This  involves  client/server
              processes  performing  rapid  connect,  send/receives  and disconnects on the local
              host.  Using epoll allows a large number of connections to be efficiently  handled,
              however,  this  can  lead  to  the connection table filling up and blocking further
              socket connections, hence impacting on the epoll bogo op stats.  For ipv4 and  ipv6
              domains,  multiple servers are spawned on multiple ports. The epoll stressor is for
              Linux only.

       --epoll-domain D
              specify the domain to use, the default is unix (aka local).  Currently  ipv4,  ipv6
              and unix are supported.

       --epoll-port P
              start  at  socket  port P. For N epoll worker processes, ports P to (P * 4) - 1 are
              used for ipv4, ipv6 domains and ports P to P - 1 are used for the unix domain.

       --epoll-ops N
              stop epoll workers after N bogo operations.

       --eventfd N
              start N parent and child worker processes that read and write 8 byte event messages
              between them via the eventfd mechanism (Linux only).

       --eventfd-ops N
              stop eventfd workers after N bogo operations.

       --exec N
              start  N  workers  continually  forking  children that exec stress-ng and then exit
              almost immediately.

       --exec-ops N
              stop exec stress workers after N bogo operations.

       --exec-max P
              create P child processes that exec stress-ng and then wait for  them  to  exit  per
              iteration.  The  default is just 1; higher values will create many temporary zombie
              processes that are waiting to be reaped. One can potentially fill  up  the  process
              table using high values for --exec-max and --exec.

       -F N, --fallocate N
              start  N  workers continually fallocating (preallocating file space) and ftuncating
              (file truncating) temporary files.  If the file is  larger  than  the  free  space,
              fallocate will produce an ENOSPC error which is ignored by this stressor.

       --fallocate-bytes N
              allocated  file  size,  the  default is 1 GB. One can specify the size as % of free
              space on the file system or in units of Bytes, KBytes, MBytes and GBytes using  the
              suffix b, k, m or g.

       --fallocate-ops N
              stop fallocate stress workers after N bogo fallocate operations.

       --fanotify N
              start  N  workers  performing  file  system  activities  such as creating, opening,
              writing, reading and unlinking files to  exercise  the  fanotify  event  monitoring
              interface (Linux only).  Each stressor runs a child process to generate file events
              and a parent process to read file events using fanotify.

       --fanotify-ops N
              stop fanotify stress workers after N bogo fanotify events.

       --fault N
              start N workers that generates minor and major page faults.

       --fault-ops N
              stop the page fault workers after N bogo page fault operations.

       --fcntl N
              start N workers that perform fcntl(2) calls with various commands.   The  exercised
              commands  (if  available) are: F_DUPFD, F_DUPFD_CLOEXEC, F_GETFD, F_SETFD, F_GETFL,
              F_SETFL, F_GETOWN, F_SETOWN, F_GETOWN_EX, F_SETOWN_EX, F_GETSIG, F_SETSIG, F_GETLK,
              F_SETLK, F_SETLKW, F_OFD_GETLK, F_OFD_SETLK and F_OFD_SETLKW.

       --fcntl-ops N
              stop the fcntl workers after N bogo fcntl operations.

       --fiemap N
              start N workers that each create a file with many randomly changing extents and has
              4 child  processes  per  worker  that  gather  the  extent  information  using  the
              FS_IOC_FIEMAP ioctl(2).

       --fiemap-ops N
              stop after N fiemap bogo operations.

       --fiemap-bytes N
              specify  the  size of the fiemap'd file in bytes.  One can specify the size as % of
              free space on the file system or in units of Bytes, KBytes, MBytes and GBytes using
              the  suffix  b,  k,  m  or g.  Larger files will contain more extents, causing more
              stress when gathering extent information.

       --fifo N
              start N workers that exercise a named pipe by transmitting 64 bit integers.

       --fifo-ops N
              stop fifo workers after N bogo pipe write operations.

       --fifo-readers N
              for each worker, create N fifo reader workers that read the named pipe using simple
              blocking reads.

       --filename N
              start  N  workers  that  exercise  file  creation  using  various  length filenames
              containing a range of allower filename characters.  This will try to see if it  can
              exceed  the  file  system allowed filename length was well as test various filename
              lengths between 1 and the maximum allowed by the file system.

       --filename-ops N
              stop filename workers after N bogo filename tests.

       --filename-opts opt
              use characters in the filename based on option 'opt'. Valid options are:

              Option           Description
              probe            default option, probe the file system for valid allowed characters
                               in a file name and use these
              posix            use  characters as specified by The Open Group Base Specifications
                               Issue 7, POSIX.1-2008, 3.278 Portable Filename Character Set

              ext              use characters allowed by  the  ext2,  ext3,  ext4  file  systems,
                               namely any 8 bit character apart from NUL and /

       --flock N
              start N workers locking on a single file.

       --flock-ops N
              stop flock stress workers after N bogo flock operations.

       -f N, --fork N
              start N workers continually forking children that immediately exit.

       --fork-ops N
              stop fork stress workers after N bogo operations.

       --fork-max P
              create  P child processes and then wait for them to exit per iteration. The default
              is just 1; higher values will create  many  temporary  zombie  processes  that  are
              waiting  to be reaped. One can potentially fill up the the process table using high
              values for --fork-max and --fork.

       --fp-error N
              start N workers that generate floating point exceptions. Computations are performed
              to  force  and  check for the FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW and
              FE_UNDERFLOW exceptions.  EDOM and ERANGE errors are also checked.

       --fp-error-ops N
              stop after N bogo floating point exceptions.

       --fstat N
              start N workers fstat'ing files in a directory (default is /dev).

       --fstat-ops N
              stop fstat stress workers after N bogo fstat operations.

       --fstat-dir directory
              specify the directory to fstat to override the default of /dev.  All the  files  in
              the directory will be fstat'd repeatedly.

       --full N
              start  N  workers  that  exercise  /dev/full.  This attempts to write to the device
              (which should always get error ENOSPC), to  read  from  the  device  (which  should
              always  return  a buffer of zeros) and to seek randomly on the device (which should
              always succeed).  (Linux only).

       --full-ops N
              stop the stress full workers after N bogo I/O operations.

       --futex N
              start N workers that rapidly exercise the futex system call. Each  worker  has  two
              processes,  a  futex  waiter  and a futex waker. The waiter waits with a very small
              timeout to stress the timeout and rapid polled  futex  waiting.  This  is  a  Linux
              specific stress option.

       --futex-ops N
              stop futex workers after N bogo successful futex wait operations.

       --get N
              start  N  workers that call system calls that fetch data from the kernel, currently
              these are: getpid, getppid, getcwd, getgid, getegid,  getuid,  getgroups,  getpgrp,
              getpgid,  getpriority, getresgid, getresuid, getrlimit, prlimit, getrusage, getsid,
              gettid, getcpu, gettimeofday, uname, adjtimex, sysfs.  Some of these  system  calls
              are OS specific.

       --get-ops N
              stop get workers after N bogo get operations.

       --getdent N
              start N workers that recursively read directories /proc, /dev/, /tmp, /sys and /run
              using getdents and getdents64 (Linux only).

       --getdent-ops N
              stop getdent workers after N bogo getdent bogo operations.

       --getrandom N
              start N workers that get 8192 random bytes from the  /dev/urandom  pool  using  the
              getrandom(2) system call (Linux) or getentropy(2) (OpenBSD).

       --getrandom-ops N
              stop getrandom workers after N bogo get operations.

       --handle N
              start  N  workers  that  exercise the name_to_handle_at(2) and open_by_handle_at(2)
              system calls. (Linux only).

       --handle-ops N
              stop after N handle bogo operations.

       -d N, --hdd N
              start N workers continually writing, reading  and  removing  temporary  files.  The
              default  mode  is to stress test sequential writes and reads.  With the --ggressive
              option enabled without any --hdd-opts options the hdd stressor  will  work  through
              all the --hdd-opt options one by one to cover a range of I/O options.

       --hdd-bytes N
              write  N  bytes for each hdd process, the default is 1 GB. One can specify the size
              as % of free space on the file system or in units  of  Bytes,  KBytes,  MBytes  and
              GBytes using the suffix b, k, m or g.

       --hdd-opts list
              specify  various  stress  test  options  as  a comma separated list. Options are as
              follows:

              Option           Description
              direct           try to minimize cache effects of the  I/O.  File  I/O  writes  are
                               performed   directly  from  user  space  buffers  and  synchronous
                               transfer is also attempted.  To guarantee  synchronous  I/O,  also
                               use the sync option.
              dsync            ensure output has been transferred to underlying hardware and file
                               metadata has been updated (using the O_DSYNC open flag).  This  is
                               equivalent   to   each  write(2)  being  followed  by  a  call  to
                               fdatasync(2). See also the fdatasync option.
              fadv-dontneed    advise kernel to expect the data will not be accessed in the  near
                               future.
              fadv-noreuse     advise kernel to expect the data to be accessed only once.
              fadv-normal      advise  kernel  there are no explicit access pattern for the data.
                               This is the default advice assumption.
              fadv-rnd         advise kernel to expect random access patterns for the data.
              fadv-seq         advise kernel to expect sequential access patterns for the data.
              fadv-willneed    advise kernel to expect the  data  to  be  accessed  in  the  near
                               future.
              fsync            flush  all  modified  in-core  data after each write to the output
                               device using an explicit fsync(2) call.
              fdatasync        similar to fsync, but do not flush the  modified  metadata  unless
                               metadata is required for later data reads to be handled correctly.
                               This uses an explicit fdatasync(2) call.
              iovec            use readv/writev multiple  buffer  I/Os  rather  than  read/write.
                               Instead  of  1  read/write operation, the buffer is broken into an
                               iovec of 16 buffers.
              noatime          do not update the file last  access  timestamp,  this  can  reduce
                               metadata writes.
              sync             ensure  output  has been transferred to underlying hardware (using
                               the O_SYNC open flag). This is equivalent to a each write(2) being
                               followed by a call to fsync(2). See also the fsync option.
              rd-rnd           read  data  randomly.  By  default, written data is not read back,
                               however, this option will force it to be read back randomly.
              rd-seq           read data sequentially. By default, written data is not read back,
                               however, this option will force it to be read back sequentially.

              syncfs           write  all buffered modifications of file metadata and data on the
                               filesystem that contains the hdd worker files.
              utimes           force update of file timestamp which may increase metadata writes.
              wr-rnd           write data randomly. The wr-seq option cannot be used at the  same
                               time.
              wr-seq           write data sequentially. This is the default if no write modes are
                               specified.

       Note that some of these options are mutually exclusive, for example, there can be only one
       method  of writing or reading.  Also, fadvise flags may be mutually exclusive, for example
       fadv-willneed cannot be used with fadv-dontneed.

       --hdd-ops N
              stop hdd stress workers after N bogo operations.

       --hdd-write-size N
              specify size of each write in bytes. Size can be from 1 byte to 4MB.

       --heapsort N
              start N workers that sort 32 bit integers using the BSD heapsort.

       --heapsort-ops N
              stop heapsort stress workers after N bogo heapsorts.

       --heapsort-size N
              specify number of 32 bit integers to sort, default is 262144 (256 × 1024).

       --hsearch N
              start N workers that search a 80% full hash table  using  hsearch(3).  By  default,
              there  are  8192 elements inserted into the hash table.  This is a useful method to
              exercise access of memory and processor cache.

       --hsearch-ops N
              stop the hsearch workers after N bogo hsearch operations are completed.

       --hsearch-size N
              specify the number of hash entries to be inserted into the hash table. Size can  be
              from 1K to 4M.

       --icache N
              start  N  workers  that  stress  the instruction cache by forcing instruction cache
              reloads.  This is achieved by modifying an instruction  cache  line,   causing  the
              processor  to  reload  it  when  we  call  a  function in inside it. Currently only
              verified and enabled for Intel x86 CPUs.

       --icache-ops N
              stop the icache workers after N bogo icache operations are completed.

       --icmp-flood N
              start N workers that flood localhost with randonly sized ICMP ping  packets.   This
              option can only be run as root.

       --icmp-flood-ops N
              stop icmp flood workers after N ICMP ping packets have been sent.

       --inode-flags N
              start   N   workers  that  exercise  inode  flags  using  the  FS_IOC_GETFLAGS  and
              FS_IOC_SETFLAGS ioctl(2). This attempts to apply all the available inode flags onto
              a directory and file even if the underlying file system may not support these flags
              (errors are just ignored).  Each worker runs 4 threads that exercise the  flags  on
              the  same  directory and file to try to force races. This is a Linux only stressor,
              see ioctl_iflags(2) for more details.

       --inode-flags-ops N
              stop the inode-flags workers after N ioctl flag setting attempts.

       --inotify N
              start  N  workers  performing  file  system  activities  such  as   making/deleting
              files/directories, moving files, etc. to stress exercise the various inotify events
              (Linux only).

       --inotify-ops N
              stop inotify stress workers after N inotify bogo operations.

       -i N, --io N
              start N workers continuously calling sync(2) to commit buffer cache to disk.   This
              can be used in conjunction with the --hdd options.

       --io-ops N
              stop io stress workers after N bogo operations.

       --iomix N
              start  N  workers  that  perform  a  mix  of  sequential,  random and memory mapped
              read/write operations as well as  forced  sync'ing  and  (if  run  as  root)  cache
              dropping.   Multiple  child  processes  are  spawned to all share a single file and
              perform different I/O operations on the same file.

       --iomix-bytes N
              write N bytes for each iomix worker process, the default is 1 GB. One  can  specify
              the size as % of free space on the file system or in units of Bytes, KBytes, MBytes
              and GBytes using the suffix b, k, m or g.

       --iomix-ops N
              stop iomix stress workers after N bogo iomix I/O operations.

       --ioprio N
              start N workers that exercise the  ioprio_get(2)  and  ioprio_set(2)  system  calls
              (Linux only).

       --ioprio-ops N
              stop after N io priority bogo operations.

       --itimer N
              start  N  workers  that  exercise  the  system  interval  timers.  This  sets up an
              ITIMER_PROF itimer that generates a SIGPROF signal.  The default frequency for  the
              itimer  is  1  MHz,  however, the Linux kernel will set this to be no more that the
              jiffy setting, hence high frequency SIGPROF signals are not normally  possible.   A
              busy loop spins on getitimer(2) calls to consume CPU and hence decrement the itimer
              based on amount of time spent in CPU and system time.

       --itimer-ops N
              stop itimer stress workers after N bogo itimer SIGPROF signals.

       --itimer-freq F
              run itimer at F Hz; range from 1 to 1000000 Hz. Normally the highest  frequency  is
              limited  by  the  number  of  jiffy  ticks  per second, so running above 1000 Hz is
              difficult to attain in practice.

       --kcmp N
              start N workers that use kcmp(2) to compare parent and child processes to determine
              if they share kernel resources (Linux only).

       --kcmp-ops N
              stop kcmp workers after N bogo kcmp operations.

       --key N
              start  N workers that create and manipulate keys using add_key(2) and ketctl(2). As
              many keys are created as the per user limit allows and then  the  following  keyctl
              commands   are   exercised   on   each  key:  KEYCTL_SET_TIMEOUT,  KEYCTL_DESCRIBE,
              KEYCTL_UPDATE, KEYCTL_READ, KEYCTL_CLEAR and KEYCTL_INVALIDATE.

       --key-ops N
              stop key workers after N bogo key operations.

       --kill N
              start N workers sending SIGUSR1 kill signals to a SIG_IGN signal handler.  Most  of
              the process time will end up in kernel space.

       --kill-ops N
              stop kill workers after N bogo kill operations.

       --klog N
              start  N workers exercising the kernel syslog(2) system call.  This will attempt to
              read the kernel log with various sized read buffers. Linux only.

       --klog-ops N
              stop klog workers after N syslog operations.

       --lease N
              start N workers locking, unlocking and breaking leases via the fcntl(2)  F_SETLEASE
              operation. The parent processes continually lock and unlock a lease on a file while
              a user selectable number of child processes open the file with a non-blocking  open
              to  generate  SIGIO  lease  breaking notifications to the parent.  This stressor is
              only available if F_SETLEASE, F_WRLCK and F_UNLCK support is provided by fcntl(2).

       --lease-ops N
              stop lease workers after N bogo operations.

       --lease-breakers N
              start N lease breaker child processes per lease  worker.   Normally  one  child  is
              plenty  to  force  many  SIGIO  lease  breaking notification signals to the parent,
              however, this option allows one to specify more child processes if required.

       --link N
              start N workers creating and removing hardlinks.

       --link-ops N
              stop link stress workers after N bogo operations.

       --lockbus N
              start N workers that rapidly lock and increment 64 bytes of randomly chosen  memory
              from  a 16MB mmap'd region (Intel x86 CPUs only).  This will cause cacheline misses
              and stalling of CPUs.

       --lockbus-ops N
              stop lockbus workers after N bogo operations.

       --locka N
              start N workers that randomly lock and unlock regions of a  file  using  the  POSIX
              advisory  locking mechanism (see fcntl(2), F_SETLK, F_GETLK). Each worker creates a
              1024 KB file and attempts to hold a maximum of 1024 concurrent locks with  a  child
              process  that also tries to hold 1024 concurrent locks. Old locks are unlocked in a
              first-in, first-out basis.

       --locka-ops N
              stop locka workers after N bogo locka operations.

       --lockf N
              start N workers that randomly lock and unlock regions of a  file  using  the  POSIX
              lockf(3) locking mechanism. Each worker creates a 64 KB file and attempts to hold a
              maximum of 1024 concurrent locks with a child process that also tries to hold  1024
              concurrent locks. Old locks are unlocked in a first-in, first-out basis.

       --lockf-ops N
              stop lockf workers after N bogo lockf operations.

       --lockf-nonblock
              instead  of  using  blocking  F_LOCK  lockf(3)  commands,  use non-blocking F_TLOCK
              commands and re-try if the lock failed.  This creates extra  system  call  overhead
              and  CPU  utilisation  as the number of lockf workers increases and should increase
              locking contention.

       --lockofd N
              start N workers that randomly lock and unlock regions of a  file  using  the  Linux
              open  file description locks (see fcntl(2), F_OFD_SETLK, F_OFD_GETLK).  Each worker
              creates a 1024 KB file and attempts to hold a maximum of 1024 concurrent locks with
              a  child  process  that  also  tries  to  hold 1024 concurrent locks. Old locks are
              unlocked in a first-in, first-out basis.

       --lockofd-ops N
              stop lockofd workers after N bogo lockofd operations.

       --longjmp N
              start N workers that exercise setjmp(3)/longjmp(3)  by  rapid  looping  on  longjmp
              calls.

       --longjmp-ops N
              stop  longjmp  stress  workers  after  N bogo longjmp operations (1 bogo op is 1000
              longjmp calls).

       --lsearch N
              start N workers that linear search a  unsorted  array  of  32  bit  integers  using
              lsearch(3).  By  default,  there  are 8192 elements in the array.  This is a useful
              method to exercise sequential access of memory and processor cache.

       --lsearch-ops N
              stop the lsearch workers after N bogo lsearch operations are completed.

       --lsearch-size N
              specify the size (number of 32 bit integers) in the array to lsearch. Size  can  be
              from 1K to 4M.

       --madvise N
              start N workers that apply random madvise(2) advise settings on pages of a 4MB file
              backed shared memory mapping.

       --madvice-ops N
              stop madvise stressors after N bogo madvise operations.

       --malloc N
              start N workers continuously calling malloc(3), calloc(3), realloc(3) and  free(3).
              By  default,  up  to  65536 allocations can be active at any point, but this can be
              altered with the --malloc-max option.  Allocation,  reallocation  and  freeing  are
              chosen  at  random;  50%  of  the  time memory is allocation (via malloc, calloc or
              realloc) and 50% of the time allocations are free'd.   Allocation  sizes  are  also
              random,  with  the maximum allocation size controlled by the --malloc-bytes option,
              the default size being 64K.  The worker is re-started if it is killed by the out of
              mememory (OOM) killer.

       --malloc-bytes N
              maximum  per allocation/reallocation size. Allocations are randomly selected from 1
              to N bytes. One can specify the size as % of total available memory or in units  of
              Bytes,  KBytes,  MBytes and GBytes using the suffix b, k, m or g.  Large allocation
              sizes cause the memory allocator to use mmap(2)  rather  than  expanding  the  heap
              using brk(2).

       --malloc-max N
              maximum  number of active allocations allowed. Allocations are chosen at random and
              placed in an allocation slot. Because about 50%/50% split  between  allocation  and
              freeing, typically half of the allocation slots are in use at any one time.

       --malloc-ops N
              stop  after  N  malloc bogo operations. One bogo operations relates to a successful
              malloc(3), calloc(3) or realloc(3).

       --malloc-thresh N
              specify the threshold where malloc uses mmap(2) instead of sbrk(2) to allocate more
              memory.  This is only available on systems that provide the GNU C mallopt(3) tuning
              function.

       --matrix N
              start N workers that perform various matrix operations on  floating  point  values.
              Testing on 64 bit x86 hardware shows that this provides a good mix of memory, cache
              and floating point operations and is an excellent way to make a CPU run hot.

              By default, this will exercise all the matrix stress methods one by one.   One  can
              specify a specific matrix stress method with the --matrix-method option.

       --matrix-ops N
              stop matrix stress workers after N bogo operations.

       --matrix-method method
              specify  a  matrix  stress method. Available matrix stress methods are described as
              follows:

              Method           Description
              all              iterate over all the below matrix stress methods
              add              add two N × N matrices
              copy             copy one N × N matrix to another
              div              divide an N × N matrix by a scalar
              hadamard         Hadamard product of two N × N matrices
              identity         create an N × N identity matrix
              frobenius        Frobenius product of two N × N matrices
              mean             arithmetic mean of two N × N matrices
              mult             multiply an N × N matrix by a scalar
              negate           negate an N × N matrix
              prod             product of two N × N matrices
              sub              subtract one N × N matrix from another N × N matrix
              trans            transpose an N × N matrix
              zero             zero an N × N matrix

       --matrix-size N
              specify the N × N size of the matrices.  Smaller values result in a floating  point
              compute  throughput  bound stressor, where as large values result in a cache and/or
              memory bandwidth bound stressor.

       --matrix-yx
              perform matrix operations in order y by x rather than the default x by y.  This  is
              suboptimal  ordering  compared  to  the  default  and  will perform more data cache
              stalls.

       --membarrier N
              start N workers that exercise the membarrier system call (Linux only).

       --membarrier-ops N
              stop membarrier stress workers after N bogo membarrier operations.

       --memcpy N
              start N workers that copy 2MB of data from  a  shared  region  to  a  buffer  using
              memcpy(3)  and  then  move  the data in the buffer with memmove(3) with 3 different
              alignments. This will exercise processor cache and system memory.

       --memcpy-ops N
              stop memcpy stress workers after N bogo memcpy operations.

       --memfd N
              start N workers that create allocations of 1024  pages  using  memfd_create(2)  and
              ftruncate(2)  for  allocation  and  mmap(2)  to map the allocation into the process
              address space.  (Linux only).

       --memfd-bytes N
              allocate N bytes per memfd stress worker, the default is 256MB. One can specify the
              size  in  as  %  of total available memory or in units of Bytes, KBytes, MBytes and
              GBytes using the suffix b, k, m or g.

       --memfd-fds N
              create N memfd file descriptors, the default is 256. One can select 8 to 4096 memfd
              file descriptions with this option.

       --memfd-ops N
              stop after N memfd-create(2) bogo operations.

       --memrate N
              start  N workers that exercise a buffer with 64, 32, 16 and 8 bit reads and writes.
              This memory stressor allows one to also specify the maximum read and  write  rates.
              The stressors will run at maximum speed if no read or write rates are specified.

       --memrate-ops N
              stop after N bogo memrate operations.

       --memrate-bytes N
              specify  the  size of the memory buffer being exercised. The default size is 256MB.
              One can specify the size in units of Bytes, KBytes, MBytes  and  GBytes  using  the
              suffix b, k, m or g.

       --memrate-rd-mbs N
              specify  the maximum allowed read rate in MB/sec. The actual read rate is dependent
              on scheduling jitter and memory accesses from other running processes.

       --memrate-wr-mbs N
              specify the maximum allowed read rate in MB/sec. The actual write rate is dependent
              on scheduling jitter and memory accesses from other running processes.

       --memthrash N
              start  N  workers that thrash and exercise a 16MB buffer in various ways to try and
              trip thermal overrun.

       --memthrash-ops N
              stop after N memthrash bogo operations.

       --memthrash-method method
              specify a memthrash stress method. Available memthrash stress methods are described
              as follows:

              Method           Description
              all              iterate over all the below memthrash methods
              chunk1           memset 1 byte chunks of random data into random locations
              chunk8           memset 8 byte chunks of random data into random locations
              chunk64          memset 64 byte chunks of random data into random locations
              chunk256         memset 256 byte chunks of random data into random locations
              chunkpage        memset page size chunks of random data into random locations
              flip             flip (invert) all bits in ramdom locations
              flush            flush cache line in random locations
              lock             lock randomly choosing locations (Intel x86 CPUs only)
              matrix           treat memory as a 2 × 2 matrix and swap random elements
              memset           memset the memory with random data
              mfence           stores with write serialization (Intel x86 CPUs only)
              prefetch         prefetch data at random memory locations
              random           randomly  run any of the memthrash methods except for 'random' and
                               'all'
              spinread         spin loop read the same random location 2^19 times
              spinwrite        spin loop write the same random location 2^19 times

       --mergesort N
              start N workers that sort 32 bit integers using the BSD mergesort.

       --mergesort-ops N
              stop mergesort stress workers after N bogo mergesorts.

       --mergesort-size N
              specify number of 32 bit integers to sort, default is 262144 (256 × 1024).

       --mincore N
              start N workers that walk through all of memory 1 page at a time  checking  of  the
              page mapped and also is resident in memory using mincore(2).

       --mincore-ops N
              stop  after  N mincore bogo operations. One mincore bogo op is equivalent to a 1000
              mincore(2) calls.  --mincore-random instead of walking through pages  sequentially,
              select  pages  at  random. The chosen address is iterated over by shifting it right
              one place and checked by mincore until the address is less or  equal  to  the  page
              size.

       --mknod N
              start  N  workers that create and remove fifos, empty files and named sockets using
              mknod and unlink.

       --mknod-ops N
              stop directory thrash workers after N bogo mknod operations.

       --mlock N
              start  N  workers  that  lock  and  unlock  memory  mapped  pages  using  mlock(2),
              munlock(2), mlockall(2) and munlockall(2). This is achieved by the mapping of three
              contiguous pages and then locking the second page,  hence  ensuring  non-contiguous
              pages  are  locked  .  This  is then repeated until the maximum allowed mlocks or a
              maximum of 262144 mappings are made.  Next, all future mappings are mlocked and the
              worker attempts to map 262144 pages, then all pages are munlocked and the pages are
              unmapped.

       --mlock-ops N
              stop after N mlock bogo operations.

       --mmap N
              start N workers continuously calling mmap(2)/munmap(2).  The initial mapping  is  a
              large   chunk  (size  specified  by  --mmap-bytes)  followed  by  pseudo-random  4K
              unmappings, then pseudo-random 4K mappings, and then linear  4K  unmappings.   Note
              that  this  can cause systems to trip the kernel OOM killer on Linux systems if not
              enough physical memory and swap is not available.  The MAP_POPULATE option is  used
              to  populate pages into memory on systems that support this.  By default, anonymous
              mappings are used, however, the --mmap-file and --mmap-async options allow  one  to
              perform file based mappings if desired.

       --mmap-ops N
              stop mmap stress workers after N bogo operations.

       --mmap-async
              enable  file  based memory mapping and use asynchronous msync'ing on each page, see
              --mmap-file.

       --mmap-bytes N
              allocate N bytes per mmap stress worker, the default is 256MB. One can specify  the
              size as % of total available memory or in units of Bytes, KBytes, MBytes and GBytes
              using the suffix b, k, m or g.

       --mmap-file
              enable file based memory mapping and by default use synchronous msync'ing  on  each
              page.

       --mmap-mprotect
              change  protection settings on each page of memory.  Each time a page or a group of
              pages are mapped or remapped then this option will make the pages read-only, write-
              only, exec-only, and read-write.

       --mmapfork N
              start  N  workers  that  each  fork  off 32 child processes, each of which tries to
              allocate some of the free memory left in  the  system  (and  trying  to  avoid  any
              swapping).   The  child processes then hint that the allocation will be needed with
              madvise(2) and then memset it to zero and hint that it is  no  longer  needed  with
              madvise before exiting.  This produces significant amounts of VM activity, a lot of
              cache misses and with minimal swapping.

       --mmapfork-ops N
              stop after N mmapfork bogo operations.

       --mmapmany N
              start N workers that attempt to  create  the  maximum  allowed  per-process  memory
              mappings.  This  is  achieved  by mapping 3 contiguous pages and then unmapping the
              middle page hence splitting the mapping into two. This is then repeated  until  the
              maximum allowed mappings or a maximum of 262144 mappings are made.

       --mmapmany-ops N
              stop after N mmapmany bogo operations.

       --mq N start  N  sender  and receiver processes that continually send and receive messages
              using POSIX message queues. (Linux only).

       --mq-ops N
              stop after N bogo POSIX message send operations completed.

       --mq-size N
              specify size of POSIX message queue. The default size is 10 messages and most Linux
              systems  this  is  the  maximum allowed size for normal users. If the given size is
              greater than the allowed message queue size  then  a  warning  is  issued  and  the
              maximum allowed size is used instead.

       --mremap N
              start N workers continuously calling mmap(2), mremap(2) and munmap(2).  The initial
              anonymous mapping is a large chunk (size  specified  by  --mremap-bytes)  and  then
              iteratively  halved  in  size by remapping all the way down to a page size and then
              back up to the original size.  This worker is only available for Linux.

       --mremap-ops N
              stop mremap stress workers after N bogo operations.

       --mremap-bytes N
              initially allocate N bytes per remap stress worker, the default is 256MB.  One  can
              specify  the  size in units of Bytes, KBytes, MBytes and GBytes using the suffix b,
              k, m or g.

       --msg N
              start N sender and receiver processes that continually send  and  receive  messages
              using System V message IPC.

       --msg-ops N
              stop after N bogo message send operations completed.

       --msync N
              start  N  stressors  that  msync data from a file backed memory mapping from memory
              back to the file and msync modified data from the file back to the  mapped  memory.
              This exercises the msync(2) MS_SYNC and MS_INVALIDATE sync operations.

       --msync-ops N
              stop after N msync bogo operations completed.

       --msync-bytes N
              allocate  N bytes for the memory mapped file, the default is 256MB. One can specify
              the size as % of total available memory or in units of Bytes,  KBytes,  MBytes  and
              GBytes using the suffix b, k, m or g.

       --netdev N
              start  N  workers  that  exercise  various  netdevice ioctl commands across all the
              available network devices. The ioctls exercised by this stressor  are  as  follows:
              SIOCGIFCONF,  SIOCGIFINDEX, SIOCGIFNAME, SIOCGIFFLAGS, SIOCGIFADDR, SIOCGIFNETMASK,
              SIOCGIFMETRIC,  SIOCGIFMTU,  SIOCGIFHWADDR,  SIOCGIFMAP  and   SIOCGIFTXQLEN.   See
              netdevice(7) for more details of these ioctl commands.

       --netdev-ops N
              stop after N netdev bogo operations completed.

       --netlink-proc N
              start  N  workers  that  spawn  child  processes and monitor fork/exec/exit process
              events via the proc netlink connector. Each event received is counted as a bogo op.
              This stressor can only be run on Linux and with root privilege.

       --netlink-proc-ops N
              stop the proc netlink connector stressors after N bogo ops.

       --nice N
              start  N  cpu  consuming  workers  that  exercise  the  available nice levels. Each
              iteration forks off a child process that runs  through  the  all  the  nice  levels
              running a busy loop for 0.1 seconds per level and then exits.

       --nice-ops N
              stop after N nice bogo nice loops

       --nop N
              start  N  workers that consume cpu cycles issuing no-op instructions. This stressor
              is available if the assembler supports the "nop" instruction.

       --nop-ops N
              stop nop workers after N no-op bogo operations. Each bogo-operation  is  equivalent
              to 256 loops of 256 no-op instructions.

       --null N
              start N workers writing to /dev/null.

       --null-ops N
              stop null stress workers after N /dev/null bogo write operations.

       --numa N
              start  N  workers  that migrate stressors and a 4MB memory mapped buffer around all
              the available NUMA nodes.  This uses migrate_pages(2) to  move  the  stressors  and
              mbind(2) and move_pages(2) to move the pages of the mapped buffer. After each move,
              the buffer is written to force activity over the bus which  results  cache  misses.
              This test will only run on hardware with NUMA enabled and more than 1 NUMA node.

       --numa-ops N
              stop NUMA stress workers after N bogo NUMA operations.

       --oom-pipe N
              start  N  workers  that  create as many pipes as allowed and exercise expanding and
              shrinking the pipes from the largest pipe size down to a page size. Data is written
              into  the  pipes and read out again to fill the pipe buffers. With the --aggressive
              mode enabled the data is not read out when the pipes are shrunk, causing the kernel
              to  OOM processes aggressively.  Running many instances of this stressor will force
              kernel to OOM processes due to the many large pipe buffer allocations.

       --oom-pipe-ops N
              stop after N bogo pipe expand/shrink operations.

       --opcode N
              start N workers that fork off children that execute randomly  generated  executable
              code.   This  will  generate  issues  such  as  illegal  instructions,  bus errors,
              segmentation faults, traps, floating point errors that are  handled  gracefully  by
              the stressor.

       --opcode-ops N
              stop after N attempts to executate illegal code.

       -o N, --open N
              start N workers that perform open(2) and then close(2) operations on /dev/zero. The
              maximum opens at one time is system defined, so  the  test  will  run  up  to  this
              maximum, or 65536 open file descriptors, which ever comes first.

       --open-ops N
              stop the open stress workers after N bogo open operations.

       --personality N
              start  N  workers  that  attempt  to  set  personality  and  get  all the available
              personality types (process execution domain types) via  the  personality(2)  system
              call. (Linux only).

       --personality-ops N
              stop personality stress workers after N bogo personality operations.

       -p N, --pipe N
              start  N  workers  that  perform  large pipe writes and reads to exercise pipe I/O.
              This exercises memory write and reads as well as context  switching.   Each  worker
              has two processes, a reader and a writer.

       --pipe-ops N
              stop pipe stress workers after N bogo pipe write operations.

       --pipe-data-size N
              specifies  the  size in bytes of each write to the pipe (range from 4 bytes to 4096
              bytes). Setting a small data size will cause more writes  to  be  buffered  in  the
              pipe,  hence  reducing  the  context  switch  rate between the pipe writer and pipe
              reader processes. Default size is the page size.

       --pipe-size N
              specifies the size of the pipe in bytes (for systems that support the  F_SETPIPE_SZ
              fcntl()  command).  Setting a small pipe size will cause the pipe to fill and block
              more frequently, hence increasing the context switch rate between the  pipe  writer
              and the pipe reader processes. Default size is 512 bytes.

       -P N, --poll N
              start  N  workers  that perform zero timeout polling via the poll(2), select(2) and
              sleep(3) calls. This wastes system and user time doing nothing.

       --poll-ops N
              stop poll stress workers after N bogo poll operations.

       --procfs N
              start N workers that  read  files  from  /proc  and  recursively  read  files  from
              /proc/self (Linux only).

       --procfs-ops N
              stop procfs reading after N bogo read operations. Note, since the number of entries
              may vary between kernels, this bogo ops metric is probably very misleading.

       --pthread N
              start N workers that iteratively creates  and  terminates  multiple  pthreads  (the
              default is 1024 pthreads per worker). In each iteration, each newly created pthread
              waits until the worker has created all the pthreads and  then  they  all  terminate
              together.

       --pthread-ops N
              stop pthread workers after N bogo pthread create operations.

       --pthread-max N
              create  N  pthreads  per  worker.  If  the product of the number of pthreads by the
              number of workers is greater than the soft  limit  of  allowed  pthreads  then  the
              maximum is re-adjusted down to the maximum allowed.

       --ptrace N
              start  N  workers  that  fork  and  trace  system  calls  of  a child process using
              ptrace(2).

       --ptrace-ops N
              stop ptracer workers after N bogo system calls are traced.

       --pty N
              start N workers that repeatedly attempt to open pseudoterminals and perform various
              pty ioctls upon the ptys before closing them.

       --pty-ops N
              stop pty workers after N pty bogo operations.

       --pty-max N
              try to open a maximum of N pseudoterminals, the default is 65536. The allowed range
              of this setting is 8..65536.

       -Q, --qsort N
              start N workers that sort 32 bit integers using qsort.

       --qsort-ops N
              stop qsort stress workers after N bogo qsorts.

       --qsort-size N
              specify number of 32 bit integers to sort, default is 262144 (256 × 1024).

       --quota N
              start N workers that exercise the Q_GETQUOTA, Q_GETFMT, Q_GETINFO,  Q_GETSTATS  and
              Q_SYNC quotactl(2) commands on all the available mounted block based file systems.

       --quota-ops N
              stop quota stress workers after N bogo quotactl operations.

       --radixsort N
              start N workers that sort random 8 byte strings using radixsort.

       --radixsort-ops N
              stop radixsort stress workers after N bogo radixsorts.

       --radixsort-size N
              specify number of strings to sort, default is 262144 (256 × 1024).

       --rdrand N
              start  N  workers  that  read  the  Intel  hardware  random number generator (Intel
              Ivybridge processors upwards).

       --rdrand-ops N
              stop rdrand stress workers after N bogo rdrand operations (1 bogo op = 2048  random
              bits successfully read).

       --readahead N
              start N workers that randomly seeks and performs 512 byte read/write I/O operations
              on a file with readahead. The default file size is 1 GB.  Readaheads and reads  are
              batched into 16 readaheads and then 16 reads.

       --readahead-bytes N
              set  the size of readahead file, the default is 1 GB. One can specify the size as %
              of free space on the file system or in units of Bytes, KBytes,  MBytes  and  GBytes
              using the suffix b, k, m or g.

       --readahead-ops N
              stop readahead stress workers after N bogo read operations.

       --remap N
              start  N  workers  that map 512 pages and re-order these pages using the deprecated
              system call remap_file_pages(2). Several page re-orderings are exercised:  forward,
              reverse, random and many pages to 1 page.

       --remap-ops N
              stop after N remapping bogo operations.

       -R N, --rename N
              start N workers that each create a file and then repeatedly rename it.

       --rename-ops N
              stop rename stress workers after N bogo rename operations.

       --resources N
              start  N workers that consume various system resources. Each worker will spawn 1024
              child processes that iterate 1024  times  consuming  shared  memory,  heap,  stack,
              temporary  files  and  various file descriptors (eventfds, memoryfds, userfaultfds,
              pipes and sockets).

       --resources-ops N
              stop after N resource child forks.

       --rlimit N
              start N workers that exceed CPU and file size resource  imits,  generating  SIGXCPU
              and SIGXFSZ signals.

       --rlimit-ops N
              stop after N bogo resource limited SIGXCPU and SIGXFSZ signals have been caught.

       --rmap N
              start N workers that exercise the VM reverse-mapping. This creates 16 processes per
              worker that write/read multiple file-backed memory mappings. There are 64 lots of 4
              page  mappings  made onto the file, with each mapping overlapping the previous by 3
              pages and at least 1 page of non-mapped memory between each of the  mappings.  Data
              is synchronously msync'd to the file 1 in every 256 iterations in a random manner.

       --rmap-ops N
              stop after N bogo rmap memory writes/reads.

       --rtc N
              start N workers that exercise the real time clock (RTC) interfaces via /dev/rtc and
              /sys/class/rtc/rtc0. No destructive writes (modifications)  are  performed  on  the
              RTC. This is a Linux only stressor.

       --rtc-ops N
              stop after N bogo RTC interface accesses.

       --schedpolicy N
              start  N  workers that work set the worker to various available scheduling policies
              out of SCHED_OTHER, SCHED_BATCH, SCHED_IDLE, SCHED_FIFO and SCHED_RR.  For the real
              time  scheduling  policies  a random sched priority is selected between the minimum
              and maximum scheduling prority settings.

       --schedpolicy-ops N
              stop after N bogo scheduling policy changes.

       --sctp N
              start N workers that perform network sctp stress activity using the Stream  Control
              Transmission  Protocol  (SCTP).   This  involves client/server processes performing
              rapid connect, send/receives and disconnects on the local host.

       --sctp-domain D
              specify the domain to use, the  default  is  ipv4.  Currently  ipv4  and  ipv6  are
              supported.

       --sctp-ops N
              stop sctp workers after N bogo operations.

       --sctp-port P
              start  at sctp port P. For N sctp worker processes, ports P to (P * 4) - 1 are used
              for ipv4, ipv6 domains and ports P to P - 1 are used for the unix domain.

       --seal N
              start N workers that exercise the fcntl(2) SEAL commands on a small anonymous  file
              created  using memfd_create(2).  After each SEAL command is issued the stessor also
              sanity checks if the seal operation has sealed the file correctly.  (Linux only).

       --seal-ops N
              stop after N bogo seal operations.

       --seccomp N
              start N workers that exercise Secure Computing system call filtering.  Each  worker
              creates  child processes that write a short message to /dev/null and then exits. 2%
              of the child processes have a seccomp filter that disallows the write  system  call
              and  hence  it  is  killed  by  seccomp with a SIGSYS.  Note that this stressor can
              generate many audit log messages each time the child is killed.

       --seccomp-ops N
              stop seccomp stress workers after N seccomp filter tests.

       --seek N
              start N workers that randomly seeks and performs 512 byte read/write I/O operations
              on a file. The default file size is 16 GB.

       --seek-ops N
              stop seek stress workers after N bogo seek operations.

       --seek-punch
              punch randomly located 8K holes into the file to cause more extents to force a more
              demanding seek stressor, (Linux only).

       --seek-size N
              specify the size of the file in bytes. Small file sizes allow the I/O to  occur  in
              the  cache, causing greater CPU load. Large file sizes force more I/O operations to
              drive causing more wait time and more I/O on the drive. One can specify the size in
              units of Bytes, KBytes, MBytes and GBytes using the suffix b, k, m or g.

       --sem N
              start  N workers that perform POSIX semaphore wait and post operations. By default,
              a parent and 4 children are started per worker to provide some  contention  on  the
              semaphore.  This  stresses  fast  semaphore  operations  and produces rapid context
              switching.

       --sem-ops N
              stop semaphore stress workers after N bogo semaphore operations.

       --sem-procs N
              start N child workers per worker  to  provide  contention  on  the  semaphore,  the
              default is 4 and a maximum of 64 are allowed.

       --sem-sysv N
              start  N  workers  that  perform  System  V  semaphore wait and post operations. By
              default, a parent and 4 children are started per worker to provide some  contention
              on  the  semaphore.  This  stresses  fast  semaphore  operations and produces rapid
              context switching.

       --sem-sysv-ops N
              stop semaphore stress workers after N bogo System V semaphore operations.

       --sem-sysv-procs N
              start N child processes per worker to provide contention on the System V semaphore,
              the default is 4 and a maximum of 64 are allowed.

       --sendfile N
              start  N workers that send an empty file to /dev/null. This operation spends nearly
              all the time in the kernel.  The  default  sendfile  size  is  4MB.   The  sendfile
              options are for Linux only.

       --sendfile-ops N
              stop sendfile workers after N sendfile bogo operations.

       --sendfile-size S
              specify the size to be copied with each sendfile call. The default size is 4MB. One
              can specify the size in units of Bytes, KBytes, MBytes and GBytes using the  suffix
              b, k, m or g.

       --shm N
              start N workers that open and allocate shared memory objects using the POSIX shared
              memory interfaces.  By default, the test will  repeatedly  create  and  destroy  32
              shared memory objects, each of which is 8MB in size.

       --shm-ops N
              stop after N POSIX shared memory create and destroy bogo operations are complete.

       --shm-bytes N
              specify  the size of the POSIX shared memory objects to be created. One can specify
              the size as % of total available memory or in units of Bytes,  KBytes,  MBytes  and
              GBytes using the suffix b, k, m or g.

       --shm-objs N
              specify the number of shared memory objects to be created.

       --shm-sysv N
              start  N  workers  that  allocate  shared  memory  using the System V shared memory
              interface.  By default, the test will repeatedly create and destroy 8 shared memory
              segments, each of which is 8MB in size.

       --shm-sysv-ops N
              stop after N shared memory create and destroy bogo operations are complete.

       --shm-sysv-bytes N
              specify  the  size  of the shared memory segment to be created. One can specify the
              size as % of total available memory or in units of Bytes, KBytes, MBytes and GBytes
              using the suffix b, k, m or g.

       --shm-sysv-segs N
              specify the number of shared memory segments to be created.

       --sigfd N
              start  N  workers  that  generate SIGRT signals and are handled by reads by a child
              process using a file descriptor set up using signalfd(2).  (Linux only). This  will
              generate a heavy context switch load when all CPUs are fully loaded.

       --sigfd-ops
              stop sigfd workers after N bogo SIGUSR1 signals are sent.

       --sigfpe N
              start N workers that rapidly cause division by zero SIGFPE faults.

       --sigfpe-ops N
              stop sigfpe stress workers after N bogo SIGFPE faults.

       --sigpending N
              start  N  workers  that  check  if SIGUSR1 signals are pending. This stressor masks
              SIGUSR1, generates a SIGUSR1 signal and uses sigpending(2) to see if the signal  is
              pending. Then it unmasks the signal and checks if the signal is no longer pending.

       --sigpending-ops N
              stop sigpending stress workers after N bogo sigpending pending/unpending checks.

       --sigsegv N
              start N workers that rapidly create and catch segmentation faults.

       --sigsegv-ops N
              stop sigsegv stress workers after N bogo segmentation faults.

       --sigsuspend N
              start  N  workers  that  each  spawn  off 4 child processes that wait for a SIGUSR1
              signal from the parent using sigsuspend(2). The parent  sends  SIGUSR1  signals  to
              each  child  in  rapid  succession.   Each sigsuspend wakeup is counted as one bogo
              operation.

       --sigsuspend-ops N
              stop sigsuspend stress workers after N bogo sigsuspend wakeups.

       --sigq N
              start N workers that rapidly  send  SIGUSR1  signals  using  sigqueue(3)  to  child
              processes that wait for the signal via sigwaitinfo(2).

       --sigq-ops N
              stop sigq stress workers after N bogo signal send operations.

       --sleep N
              start  N  workers that spawn off multiple threads that each perform multiple sleeps
              of  ranges  1us  to  0.1s.   This  creates  multiple  context  switches  and  timer
              interrupts.

       --sleep-ops N
              stop after N sleep bogo operations.

       --sleep-max P
              start P threads per worker. The default is 1024, the maximum allowed is 30000.

       -S N, --sock N
              start  N  workers that perform various socket stress activity. This involves a pair
              of  client/server  processes  performing  rapid  connect,  send  and  receives  and
              disconnects on the local host.

       --sock-domain D
              specify  the  domain to use, the default is ipv4. Currently ipv4, ipv6 and unix are
              supported.

       --sock-nodelay
              This disables the TCP Nagle algorithm, so data segments are always sent as soon  as
              possible.   This  stops  data  from  being buffered before being transmitted, hence
              resulting in poorer network utilisation  and  more  context  switches  between  the
              sender and receiver.

       --sock-port P
              start at socket port P. For N socket worker processes, ports P to P - 1 are used.

       --sock-ops N
              stop socket stress workers after N bogo operations.

       --sock-opts [ send | sendmsg | sendmmsg ]
              by  default, messages are sent using send(2). This option allows one to specify the
              sending method using send(2), sendmsg(2) or sendmmsg(2).   Note  that  sendmmsg  is
              only available for Linux systems that support this system call.

       --sock-type [ stream | seqpacket ]
              specify  the  socket  type  to use. The default type is stream. seqpacket currently
              only works for the unix socket domain.

       --sockdiag N
              start N workers that exercise the Linux sock_diag netlink socket diagnostics (Linux
              only).   This  currently requests dianostics using UDIAG_SHOW_NAME, UDIAG_SHOW_VFS,
              UDIAG_SHOW_PEER, UDIAG_SHOW_ICONS, UDIAG_SHOW_RQLEN and UDIAG_SHOW_MEMINFO for  the
              AF_UNIX family of socket connections.

       --sockdiag-ops N
              stop after receiving N sock_diag diagnostic messages.

       --sockfd N
              start  N  workers  that  pass  file descriptors over a UNIX domain socket using the
              CMSG(3) ancillary data mechanism. For each worker, pair of client/server  processes
              are created, the server opens as many file descriptors on /dev/null as possible and
              passing these over the socket to a client that reads these from the CMSG  data  and
              immediately closes the files.

       --sockfd-ops N
              stop sockfd stress workers after N bogo operations.

       --sockfd-port P
              start at socket port P. For N socket worker processes, ports P to P - 1 are used.

       --sockpair N
              start  N  workers that perform socket pair I/O read/writes. This involves a pair of
              client/server processes performing randomly sized socket I/O operations.

       --sockpair-ops N
              stop socket pair stress workers after N bogo operations.

       --softlockup N
              start N workers that flip between  with  the  "real-time"  SCHED_FIO  and  SCHED_RR
              scheduling  policies at the highest priority to force softlockups. This can only be
              run as root and for best results the number of stressors should  be  at  least  the
              number  of online CPUs. Once running, this is practically impossible to stop and it
              will force softlockup issues and may trigger watchdog timeout reboots.

       --softlockup-ops N
              stop softlockup stress workers after N bogo scheduler policy changes.

       --spawn N
              start N workers continually spawn children using posix_spawn(3) that exec stress-ng
              and then exit almost immediately. Currently Linux only.

       --spawn-ops N
              stop spawn stress workers after N bogo spawns.

       --splice N
              move  data  from  /dev/zero to /dev/null through a pipe without any copying between
              kernel address space and user address space using splice(2). This is only available
              for Linux.

       --splice-ops N
              stop after N bogo splice operations.

       --splice-bytes N
              transfer N bytes per splice call, the default is 64K. One can specify the size as %
              of total available memory or in units of Bytes, KBytes, MBytes and GBytes using the
              suffix b, k, m or g.

       --stack N
              start N workers that rapidly cause and catch stack overflows by use of alloca(3).

       --stack-fill
              the  default  action  is  to  touch  the lowest page on each stack allocation. This
              option touches all the pages by filling the new stack allocation with  zeros  which
              forces physical pages to be allocated and hence is more aggressive.

       --stack-ops N
              stop stack stress workers after N bogo stack overflows.

       --stackmmap N
              start N workers that use a 2MB stack that is memory mapped onto a temporary file. A
              recursive function works down the stack and flushes dirty stack pages back  to  the
              memory  mapped  file  using  msync(2)  until the end of the stack is reached (stack
              overflow). This exercises dirty page and stack exception handling.

       --stackmmap-ops N
              stop workers after N stack overflows have occurred.

       --str N
              start N workers that exercise various libc string functions on random strings.

       --str-method strfunc
              select a specific libc string function to stress.  Available  string  functions  to
              stress  are:  all,  index,  rindex,  strcasecmp,  strcat,  strchr, strcoll, strcmp,
              strcpy, strlen, strncasecmp, strncat, strncmp, strrchr and strxfrm.  See  string(3)
              for  more  information  on these string functions.  The 'all' method is the default
              and will exercise all the string methods.

       --str-ops N
              stop after N bogo string operations.

       --stream N
              start N workers exercising a memory bandwidth stressor loosely based on the  STREAM
              "Sustainable  Memory  Bandwidth in High Performance Computers" benchmarking tool by
              John D. McCalpin, Ph.D.  This stressor allocates buffers that are at least 4  times
              the  size  of  the  CPU  L2  cache  and  continually  performs  rounds of following
              computations on large arrays of double precision floating point numbers:

              Operation            Description
              copy                 c[i] = a[i]
              scale                b[i] = scalar * c[i]
              add                  c[i] = a[i] + b[i]
              triad                a[i] = b[i] + (c[i] * scalar)

              Since this is loosely based on a variant of  the  STREAM  benchmark  code,  DO  NOT
              submit  results  based  on  this  as  it is intended to in stress-ng just to stress
              memory and compute  and  NOT  intended  for  STREAM  accurate  tuned  or  non-tuned
              benchmarking  whatsoever.   Use the official STREAM benchmarking tool if you desire
              accurate and standardised STREAM benchmarks.

       --stream-ops N
              stop after N stream bogo operations, where a bogo operation is one round  of  copy,
              scale, add and triad operations.

       --stream-l3-size N
              Specify  the CPU Level 3 cache size in bytes.  One can specify the size in units of
              Bytes, KBytes, MBytes and GBytes using the suffix b, k, m or g.  If  the  L3  cache
              size  is not provided, then stress-ng will attempt to determine the cache size, and
              failing this, will default the size to 4MB.

       --stream-madvise [ hugepage | nohugepage | normal ]
              Specify the madvise options used on the memory mapped buffer  used  in  the  stream
              stressor. Non-linux systems will only have the 'normal' madvise advice. The default
              is 'normal'.

       --swap N
              start N workers that add and remove small randomly  sizes  swap  partitions  (Linux
              only).  Note that if too many swap partitions are added then the stressors may exit
              with exit code 3 (not enough resources).

       --swap-ops N
              stop the swap workers after N swapon/swapoff iterations.

       -s N, --switch N
              start N workers that send messages via pipe to a child to force context switching.

       --switch-ops N
              stop context switching workers after N bogo operations.

       --symlink N
              start N workers creating and removing symbolic links.

       --symlink-ops N
              stop symlink stress workers after N bogo operations.

       --sync-file N
              start  N  workers  that  perform  a  range  of  data  syncs  across  a  file  using
              sync_file_range(2).   Three  mixes of syncs are performed, from start to the end of
              the file,  from end of the file to the start, and a random mix. A random  selection
              of   valid   sync   types   are  used,  covering  the  SYNC_FILE_RANGE_WAIT_BEFORE,
              SYNC_FILE_RANGE_WRITE and SYNC_FILE_RANGE_WAIT_AFTER flag bits.

       --sync-file-ops N
              stop sync-file workers after N bogo sync operations.

       --sync-file-bytes N
              specify the size of the file to be sync'd. One can specify the size as  %  of  free
              space  on  the  file  system in units of Bytes, KBytes, MBytes and GBytes using the
              suffix b, k, m or g.

       --sysinfo N
              start N workers that continually read  system  and  process  specific  information.
              This  reads  the process user and system times using the times(2) system call.  For
              Linux systems, it also reads overall system statistics using the sysinfo(2)  system
              call  and  also  the  file  system  statistics  for  all mounted file systems using
              statfs(2).

       --sysinfo-ops N
              stop the sysinfo workers after N bogo operations.

       --sysfs N
              start N workers that recursively read files from /sys (Linux only).  This may cause
              specific kernel drivers to emit messages into the kernel log.

       --sys-ops N
              stop  sysfs reading after N bogo read operations. Note, since the number of entries
              may vary between kernels, this bogo ops metric is probably very misleading.

       --tee N
              move data from a writer process to a reader process through pipes and to  /dev/null
              without  any  copying  between  kernel  address  space and user address space using
              tee(2). This is only available for Linux.

       --tee-ops N
              stop after N bogo tee operations.

       -T N, --timer N
              start N workers creating timer events at a default rate of 1 MHz (Linux only); this
              can  create  a many thousands of timer clock interrupts. Each timer event is caught
              by a signal handler and counted as a bogo timer op.

       --timer-ops N
              stop timer stress workers after N bogo timer events (Linux only).

       --timer-freq F
              run timers at F Hz; range from 1 to 1000000000 Hz (Linux  only).  By  selecting  an
              appropriate  frequency  stress-ng  can generate hundreds of thousands of interrupts
              per second.

       --timer-rand
              select a timer frequency based around the timer frequency +/- 12.5% random  jitter.
              This  tries  to force more variability in the timer interval to make the scheduling
              less predictable.

       --timerfd N
              start N workers creating timerfd events at a default rate of 1  MHz  (Linux  only);
              this can create a many thousands of timer clock events. Timer events are waited for
              on the timer file descriptor using select(2) and then read and counted  as  a  bogo
              timerfd op.

       --timerfd-ops N
              stop timerfd stress workers after N bogo timerfd events (Linux only).

       --timerfd-freq F
              run  timers  at  F  Hz; range from 1 to 1000000000 Hz (Linux only). By selecting an
              appropriate frequency stress-ng can generate hundreds of  thousands  of  interrupts
              per second.

       --timerfd-rand
              select  a  timerfd  frequency  based  around  the  timer frequency +/- 12.5% random
              jitter. This tries to force more variability in the  timer  interval  to  make  the
              scheduling less predictable.

       --tlb-shootdown N
              start  N workers that force Translation Lookaside Buffer (TLB) shootdowns.  This is
              achieved by creating up to 16 child processes that all share a region of memory and
              these  processes  are  shared amongst the available CPUs.  The processes adjust the
              page mapping settings causing TLBs to be force flushed  on  the  other  processors,
              causing the TLB shootdowns.

       --tlb-shootdown-ops N
              stop after N bogo TLB shootdown operations are completed.

       --tmpfs N
              start  N workers that create a temporary file on an available tmpfs file system and
              perform various file based mmap operations upon it.

       --tmpfs-ops N
              stop tmpfs stressors after N bogo mmap operations.

       --tsc N
              start N workers that read the Time Stamp Counter (TSC) 256 times per loop iteration
              (bogo operation). Available only on Intel x86 platforms.

       --tsc-ops N
              stop the tsc workers after N bogo operations are completed.

       --tsearch N
              start  N  workers  that  insert, search and delete 32 bit integers on a binary tree
              using tsearch(3), tfind(3) and tdelete(3). By default, there are  65536  randomized
              integers  used  in  the tree.  This is a useful method to exercise random access of
              memory and processor cache.

       --tsearch-ops N
              stop the tsearch workers after N bogo tree operations are completed.

       --tsearch-size N
              specify the size (number of 32 bit integers) in the array to tsearch. Size  can  be
              from 1K to 4M.

       --udp N
              start N workers that transmit data using UDP. This involves a pair of client/server
              processes performing rapid connect, send and receives and disconnects on the  local
              host.

       --udp-domain D
              specify  the  domain to use, the default is ipv4. Currently ipv4, ipv6 and unix are
              supported.

       --udp-lite
              use the UDP-Lite (RFC 3828) protocol (only for ipv4 and ipv4 domains).

       --udp-ops N
              stop udp stress workers after N bogo operations.

       --udp-port P
              start at port P. For N udp worker processes, ports P to P - 1 are used. By default,
              ports 7000 upwards are used.

       --udp-flood N
              start  N  workers  that attempt to flood the host with UDP packets to random ports.
              The IP address of the packets are currently not spoofed. This is only available  on
              systems that support AF_PACKET.

       --udp-flood-domain D
              specify  the  domain  to  use,  the  default  is  ipv4. Currently ipv4 and ipv6 are
              supported.

       --udp-flood-ops N
              stop udp-flood stress workers after N bogo operations.

       --unshare N
              start N workers that each fork off 32 child processes, each of which exercises  the
              unshare(2)  system  call  by disassociating parts of the process execution context.
              (Linux only).

       --unshare-ops N
              stop after N bogo unshare operations.

       -u N, --urandom N
              start N workers reading /dev/urandom (Linux only). This will load the kernel random
              number source.

       --urandom-ops N
              stop urandom stress workers after N urandom bogo read operations (Linux only).

       --userfaultfd N
              start  N  workers  that  generate  write  page faults on a small anonymously mapped
              memory region and handle these faults using the user space fault handling  via  the
              userfaultfd mechanism.  This will generate a large quanity of major page faults and
              also context switches during the handling of the page faults.  (Linux only).

       --userfaultfd-ops N
              stop userfaultfd stress workers after N page faults.

       --userfaultfd-bytes N
              mmap N bytes per userfaultfd worker to page fault on, the default is 16MB.  One can
              specify  the  size  as  %  of  total available memory or in units of Bytes, KBytes,
              MBytes and GBytes using the suffix b, k, m or g.

       --utime N
              start N workers updating file timestamps. This is mainly CPU bound when the default
              is used as the system flushes metadata changes only periodically.

       --utime-ops N
              stop utime stress workers after N utime bogo operations.

       --utime-fsync
              force  metadata  changes on each file timestamp update to be flushed to disk.  This
              forces the test to become I/O bound and will result in many dirty metadata writes.

       --vecmath N
              start N workers that perform various unsigned integer math  operations  on  various
              128  bit  vectors.  A  mix of vector math operations are performed on the following
              vectors: 16 × 8 bits, 8 × 16 bits, 4 × 32 bits, 2 × 64 bits. The  metrics  produced
              by  this mix depend on the processor architecture and the vector math optimisations
              produced by the compiler.

       --vecmath-ops N
              stop after N bogo vector integer math operations.

       --vfork N
              start N workers continually vforking children that immediately exit.

       --vfork-ops N
              stop vfork stress workers after N bogo operations.

       --vfork-max P
              create P processes and then wait for them to exit per  iteration.  The  default  is
              just  1; higher values will create many temporary zombie processes that are waiting
              to be reaped. One can potentially fill up the the process table using  high  values
              for --vfork-max and --vfork.

       --vforkmany N
              start  N  workers  that spawn off a chain of vfork children until the process table
              fills up and/or vfork fails.  vfork can rapidly  create  child  processes  and  the
              parent  process has to wait until the child dies, so this stressor rapidly fills up
              the process table.

       --vforkmany-ops N
              stop vforkmany stressors after N vforks have been made.

       -m N, --vm N
              start N workers continuously calling mmap(2)/munmap(2) and writing to the allocated
              memory.  Note  that  this  can cause systems to trip the kernel OOM killer on Linux
              systems if not enough physical memory and swap is not available.

       --vm-bytes N
              mmap N bytes per vm worker, the default is 256MB. One can specify the size as %  of
              total  available  memory  or in units of Bytes, KBytes, MBytes and GBytes using the
              suffix b, k, m or g.

       --vm-ops N
              stop vm workers after N bogo operations.

       --vm-hang N
              sleep N seconds before unmapping memory, the default is zero seconds.  Specifying 0
              will do an infinite wait.

       --vm-keep
              do not continually unmap and map memory, just keep on re-writing to it.

       --vm-locked
              Lock  the pages of the mapped region into memory using mmap MAP_LOCKED (since Linux
              2.5.37).  This is similar to locking memory as described in mlock(2).

       --vm-madvise advice
              Specify the madvise 'advice' option used on the memory mapped regions used  in  the
              vm  stressor.  Non-linux  systems will only have the 'normal' madvise advice, linux
              systems support  'dontneed',  'hugepage',  'mergeable'  ,  'nohugepage',  'normal',
              'random',  'sequential', 'unmergeable' and 'willneed' advice. If this option is not
              used then the default is to pick random madvise advice  for  each  mmap  call.  See
              madvise(2) for more details.

       --vm-method m
              specify  a  vm  stress  method.  By  default,  all the stress methods are exercised
              sequentially, however one can specify just one method to be used if required.  Each
              of the vm workers have 3 phases:

              1. Initialised. The anonymously memory mapped region is set to a known pattern.

              2.  Exercised. Memory is modified in a known predictable way. Some vm workers alter
              memory sequentially, some use small or large strides to step along memory.

              3. Checked. The modified memory is checked  to  see  if  it  matches  the  expected
              result.

              The  vm methods containing 'prime' in their name have a stride of the largest prime
              less than 2^64, allowing to them to thoroughly step through memory  and  touch  all
              locations  just  once  while  also doing without touching memory cells next to each
              other. This strategy exercises the cache and page non-locality.

              Since the memory being exercised is virtually mapped then there is no guarantee  of
              touching page addresses in any particular physical order.  These workers should not
              be used to test that all the system's memory is working correctly either, use tools
              such as memtest86 instead.

              The  vm  stress  methods  are  intended to exercise memory in ways to possibly find
              memory issues and to try to force thermal errors.

              Available vm stress methods are described as follows:

              Method                  Description
              all                     iterate over all the vm stress methods as listed below.
              flip                    sequentially work through memory 8 times,  each  time  just
                                      one bit in memory flipped (inverted). This will effectively
                                      invert each byte in 8 passes.
              galpat-0                galloping pattern zeros. This sets all bits to 0 and  flips
                                      just  1  in 4096 bits to 1. It then checks to see if the 1s
                                      are pulled  down  to  0  by  their  neighbours  or  of  the
                                      neighbours have been pulled up to 1.
              galpat-1                galloping  pattern  ones. This sets all bits to 1 and flips
                                      just 1 in 4096 bits to 0. It then checks to see if  the  0s
                                      are pulled up to 1 by their neighbours or of the neighbours
                                      have been pulled down to 0.
              gray                    fill the memory with  sequential  gray  codes  (these  only
                                      change  1  bit  at  a time between adjacent bytes) and then
                                      check if they are set correctly.
              incdec                  work sequentially through  memory  twice,  the  first  pass
                                      increments  each  byte  by  a specific value and the second
                                      pass decrements each byte back to the original start value.
                                      The increment/decrement value changes on each invocation of
                                      the stressor.
              inc-nybble              initialise memory to a set  value  (that  changes  on  each
                                      invocation  of  the  stressor)  and  then sequentially work
                                      through each byte incrementing the bottom 4 bits by  1  and
                                      the top 4 bits by 15.
              rand-set                sequentially  work  through memory in 64 bit chunks setting
                                      bytes in the chunk to the same 8  bit  random  value.   The
                                      random  value changes on each chunk.  Check that the values
                                      have not changed.
              rand-sum                sequentially set all  memory  to  random  values  and  then
                                      summate  the  number  of  bits  that  have changed from the
                                      original set values.
              read64                  sequentially read memory using 32 x 64 bit reads  per  bogo
                                      loop.  Each  loop  equates  to  one  bogo  operation.  This
                                      exercises raw memory reads.

              ror                     fill memory with a random  pattern  and  then  sequentially
                                      rotate  64  bits of memory right by one bit, then check the
                                      final load/rotate/stored values.
              swap                    fill memory in 64 byte chunks with  random  patterns.  Then
                                      swap  each  64 chunk with a randomly chosen chunk. Finally,
                                      reverse the swap to put the chunks back to  their  original
                                      place  and  check  if  the  data is correct. This exercises
                                      adjacent and random memory load/stores.
              move-inv                sequentially fill memory 64 bits of memory at a  time  with
                                      random  values,  and  then  check  if  the  memory  is  set
                                      correctly.  Next, sequentially invert each 64  bit  pattern
                                      and again check if the memory is set as expected.
              modulo-x                fill  memory  over 23 iterations. Each iteration starts one
                                      byte further along from the start of the memory  and  steps
                                      along in 23 byte strides. In each stride, the first byte is
                                      set to a random pattern and all other bytes are set to  the
                                      inverse.  Then it checks see if the first byte contains the
                                      expected random pattern. This exercises  cache  store/reads
                                      as  well  as  seeing  if  neighbouring cells influence each
                                      other.
              prime-0                 iterate 8 times by stepping through memory  in  very  large
                                      prime strides clearing just on bit at a time in every byte.
                                      Then check to see if all bits are set to zero.
              prime-1                 iterate 8 times by stepping through memory  in  very  large
                                      prime  strides setting just on bit at a time in every byte.
                                      Then check to see if all bits are set to one.
              prime-gray-0            first step through  memory  in  very  large  prime  strides
                                      clearing  just on bit (based on a gray code) in every byte.
                                      Next, repeat this but clear the other 7 bits. Then check to
                                      see if all bits are set to zero.
              prime-gray-1            first  step  through  memory  in  very  large prime strides
                                      setting just on bit (based on a gray code) in  every  byte.
                                      Next,  repeat  this but set the other 7 bits. Then check to
                                      see if all bits are set to one.
              rowhammer               try to force memory corruption using the  rowhammer  memory
                                      stressor.  This fetches two 32 bit integers from memory and
                                      forces a cache flush on the two addresses  multiple  times.
                                      This has been known to force bit flipping on some hardware,
                                      especially with lower frequency memory refresh cycles.
              walk-0d                 for each byte  in  memory,  walk  through  each  data  line
                                      setting them to low (and the others are set high) and check
                                      that the written value is as expected. This checks  if  any
                                      data lines are stuck.
              walk-1d                 for  each  byte  in  memory,  walk  through  each data line
                                      setting them to high (and the others are set low) and check
                                      that  the  written value is as expected. This checks if any
                                      data lines are stuck.
              walk-0a                 in the given  memory  mapping,  work  through  a  range  of
                                      specially chosen addresses working through address lines to
                                      see if any address lines are stuck  low.  This  works  best
                                      with  physical memory addressing, however, exercising these
                                      virtual addresses has some value too.
              walk-1a                 in the given  memory  mapping,  work  through  a  range  of
                                      specially chosen addresses working through address lines to
                                      see if any address lines are stuck high.  This  works  best
                                      with  physical memory addressing, however, exercising these
                                      virtual addresses has some value too.
              write64                 sequentially write memory using 32 x 64 bit writes per bogo
                                      loop.  Each  loop  equates  to  one  bogo  operation.  This
                                      exercises raw memory writes.  Note that memory  writes  are
                                      not checked at the end of each test iteration.
              zero-one                set  all memory bits to zero and then check if any bits are
                                      not zero. Next, set all the memory bits to one and check if
                                      any bits are not one.

       --vm-populate
              populate  (prefault) page tables for the memory mappings; this can stress swapping.
              Only available on systems that support MAP_POPULATE (since Linux 2.5.46).

       --vm-rw N
              start   N   workers   that   transfer   memory   to/from   a   parent/child   using
              process_vm_writev(2)  and process_vm_readv(2). This is feature is only supported on
              Linux.  Memory transfers are only verified if the --verify option is enabled.

       --vm-rw-ops N
              stop vm-rw workers after N memory read/writes.

       --vm-rw-bytes N
              mmap N bytes per vm-rw worker, the default is 16MB. One can specify the size  as  %
              of total available memory or in units of Bytes, KBytes, MBytes and GBytes using the
              suffix b, k, m or g.

       --vm-splice N
              move data from memory to /dev/null through  a  pipe  without  any  copying  between
              kernel  address space and user address space using vmsplice(2) and splice(2).  This
              is only available for Linux.

       --vm-splice-ops N
              stop after N bogo vm-splice operations.

       --vm-splice-bytes N
              transfer N bytes per vmsplice call, the default is 64K. One can specify the size as
              %  of  total available memory or in units of Bytes, KBytes, MBytes and GBytes using
              the suffix b, k, m or g.

       --wait N
              start N workers that spawn off two children; one spins  in  a  pause(2)  loop,  the
              other  continually  stops and continues the first. The controlling process waits on
              the first child to be resumed by the  delivery  of  SIGCONT  using  waitpid(2)  and
              waitid(2).

       --wait-ops N
              stop after N bogo wait operations.

       --wcs N
              start  N  workers  that  exercise  various  libc wide character string functions on
              random strings.

       --wcs-method wcsfunc
              select a specific libc wide character string function to stress.  Available  string
              functions  to stress are: all, wcscasecmp, wcscat, wcschr, wcscoll, wcscmp, wcscpy,
              wcslen, wcsncasecmp, wcsncat, wcsncmp, wcsrchr and wcsxfrm.  The  'all'  method  is
              the default and will exercise all the string methods.

       --wcs-ops N
              stop after N bogo wide character string operations.

       --xattr N
              start  N workers that create, update and delete batches of extended attributes on a
              file.

       --xattr-ops N
              stop after N bogo extended attribute operations.

       -y N, --yield N
              start N workers that call sched_yield(2). This stressor ensures  that  at  least  2
              child  processes  per  CPU  exercice shield_yield(2) no matter how many workers are
              specified, thus always ensuring rapid context switching.

       --yield-ops N
              stop yield stress workers after N sched_yield(2) bogo operations.

       --zero N
              start N workers reading /dev/zero.

       --zero-ops N
              stop zero stress workers after N /dev/zero bogo read operations.

       --zlib N
              start N workers compressing and decompressing random data using zlib.  Each  worker
              has  two processes, one that compresses random data and pipes it to another process
              that decompresses the data. This stressor exercises CPU, cache and memory.

       --zlib-ops N
              stop after N bogo compression operations, each  bogo  compression  operation  is  a
              compression of 64K of random data at the highest compression level.

       --zlib-method method
              specify  the type of random data to send to the zlib library.  By default, the data
              stream is created  from  a  random  selection  of  the  different  data  generation
              processes.   However  one  can  specify  just  one  method  to be used if required.
              Available zlib data generation methods are described as follows:

              Method           Description
              00ff             randomly distributed 0x00 and 0xFF values
              ascii01          randomly distributed ASCII 0 and 1 characters
              asciidigits      randomly distributed ASCII digits in the range of 0 and 9
              binary           32 bit random numbers
              fixed            data stream is repeated 0x04030201
              latin            Random latin sentences from a sample of Lorem Ipsum text.
              nybble           randomly distributed bytes in the range of 0x00 to 0x0f
              objcode          object code selected from a random start point  in  the  stress-ng
                               text segment

              random           segments  of  the  data stream are created by randomly calling the
                               different data generation methods.
              rarely1          data that has a single 1 in every 32 bits, randomly located
              rarely0          data that has a single 0 in every 32 bits, randomly located
              text             random ASCII text

       --zombie N
              start N workers that create zombie processes. This will rapidly  try  to  create  a
              default  of  8192  child  processes that immediately die and wait in a zombie state
              until they are reaped.  Once the maximum number of processes is  reached  (or  fork
              fails  because  one  has reached the maximum allowed number of children) the oldest
              child is reaped and a new process is then created in a first-in  first-out  manner,
              and then repeated.

       --zombie-ops N
              stop zombie stress workers after N bogo zombie operations.

       --zombie-max N
              try  to create as many as N zombie processes. This may not be reached if the system
              limit is less than N.

EXAMPLES

       stress-ng --vm 8 --vm-bytes 80% -t 1h

              run 8 virtual memory stressors that combined use 80% of the available memory for  1
              hour. Thus each stressor uses 10% of the available memory.

       stress-ng --cpu 4 --io 2 --vm 1 --vm-bytes 1G --timeout 60s

              runs  for  60  seconds with 4 cpu stressors, 2 io stressors and 1 vm stressor using
              1GB of virtual memory.

       stress-ng --iomix 2 --iomix-bytes 10% -t 10m

              runs 2 instances of the mixed I/O stressors using a total of 10% of  the  available
              file  system  space for 10 minutes. Each stressor will use 5% of the available file
              system space.

       stress-ng  --cyclic  1  --cyclic-dist  2500  --cyclic-method  clock_ns  --cyclic-prio  100
       --cyclic-sleep 10000 --hdd 0 -t 1m

              measures  real time scheduling latencies created by the hdd stressor. This uses the
              high resolution nanosecond clock to  measure  latencies  during  sleeps  of  10,000
              nanoseconds.  At  the  end  of 1 minute of stressing, the latency distribution with
              2500 ns intervals will be displayed.  NOTE:  this  must  be  run  with  super  user
              privileges to enable the real time scheduling to get accurate measurements.

       stress-ng --cpu 8 --cpu-ops 800000

              runs 8 cpu stressors and stops after 800000 bogo operations.

       stress-ng --sequential 2 --timeout 2m --metrics

              run 2 simultaneous instances of all the stressors sequentially one by one, each for
              2 minutes and summarise with performance metrics at the end.

       stress-ng --cpu 4 --cpu-method fft --cpu-ops 10000 --metrics-brief

              run 4 FFT cpu stressors, stop after 10000 bogo operations  and  produce  a  summary
              just for the FFT results.

       stress-ng --cpu 0 --cpu-method all -t 1h

              run  cpu  stressors  on  all  online  CPUs  working  through  all the available CPU
              stressors for 1 hour.

       stress-ng --all 4 --timeout 5m

              run 4 instances of all the stressors for 5 minutes.

       stress-ng --random 64

              run 64 stressors that are randomly chosen from all the available stressors.

       stress-ng --cpu 64 --cpu-method all --verify -t 10m --metrics-brief

              run  64  instances  of  all  the  different  cpu  stressors  and  verify  that  the
              computations are correct for 10 minutes with a bogo operations summary at the end.

       stress-ng --sequential 0 -t 10m

              run  all  the  stressors one by one for 10 minutes, with the number of instances of
              each stressor matching the number of online CPUs.

       stress-ng --sequential 8 --class io -t 5m --times

              run all the stressors in the io class one  by  one  for  5  minutes  each,  with  8
              instances  of  each stressor running concurrently and show overall time utilisation
              statistics at the end of the run.

       stress-ng --all 0 --maximize --aggressive

              run all the stressors (1 instance of each per  CPU)  simultaneously,  maximize  the
              settings   (memory   sizes,   file   allocations,   etc.)   and   select  the  most
              demanding/aggressive options.

       stress-ng --random 32 -x numa,hdd,key

              run 32 randomly selected stressors and exclude the numa, hdd and key stressors

       stress-ng --sequential 4 --class vm --exclude bigheap,brk,stack

              run 4 instances of the VM stressors one after each other,  excluding  the  bigheap,
              brk and stack stressors

       stress-ng --taskset 0,2-3 --cpu 3

              run 3 instances of the CPU stressor and pin them to CPUs 0, 2 and 3.

EXIT STATUS

         Status     Description
           0        Success.
           1        Error;  incorrect  user  options  or  a fatal resource issue in the stress-ng
                    stressor harness (for example, out of memory).
           2        One or more stressors failed.
           3        One or more stressors failed to initialise because of lack of resources,  for
                    example  ENOMEM (no memory), ENOSPC (no space on file system) or a missing or
                    unimplemented system call.
           4        One or more stressors were not implemented  on  a  specific  architecture  or
                    operating system.
           5        A stressor has been killed by an unexpected signal

BUGS

       File bug reports at:
         https://launchpad.net/ubuntu/+source/stress-ng/+filebug

SEE ALSO

       cpuburn(1), perf(1), stress(1), taskset(1)

AUTHOR

       stress-ng  was  written  by  Colin King <colin.king@canonical.com> and is a clean room re-
       implementation  and  extension  of  the   original   stress   tool   by   Amos   Waterland
       <apw@rossby.metr.ou.edu>.  Thanks  also  for  contributions  from  Abdul Haleem, Christian
       Ehrhardt, James Hunt, Jim Rowan, Joseph DeVincentis, Luca Pizzamiglio, Luis Henriques, Rob
       Colclaser, Tim Gardner and Zhiyi Sun.

NOTES

       Sending  a  SIGALRM, SIGINT or SIGHUP to stress-ng causes it to terminate all the stressor
       processes and ensures temporary files and shared memory segments are removed cleanly.

       Sending a SIGUSR2 to  stress-ng  will  dump  out  the  current  load  average  and  memory
       statistics.

       Note  that  the  stress-ng  cpu, io, vm and hdd tests are different implementations of the
       original stress tests and hence may produce different stress  characteristics.   stress-ng
       does not support any GPU stress tests.

       The  bogo  operations  metrics  may  change with each release  because of bug fixes to the
       code, new features, compiler optimisations or changes in system call performance.

COPYRIGHT

       Copyright © 2013-2017 Canonical Ltd.
       This is free software; see the source for copying conditions.  There is NO  warranty;  not
       even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

                                        September 13, 2017                           STRESS-NG(1)