Provided by: linux-tools-common_4.18.0-10.11_all bug

NAME

       perf-top - System profiling tool.

SYNOPSIS

       perf top [-e <EVENT> | --event=EVENT] [<options>]

DESCRIPTION

       This command generates and displays a performance counter profile in real time.

OPTIONS

       -a, --all-cpus
           System-wide collection. (default)

       -c <count>, --count=<count>
           Event period to sample.

       -C <cpu-list>, --cpu=<cpu>
           Monitor only on the list of CPUs provided. Multiple CPUs can be provided as a
           comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0-2.
           Default is to monitor all CPUS.

       -d <seconds>, --delay=<seconds>
           Number of seconds to delay between refreshes.

       -e <event>, --event=<event>
           Select the PMU event. Selection can be a symbolic event name (use perf list to list
           all events) or a raw PMU event (eventsel+umask) in the form of rNNN where NNN is a
           hexadecimal event descriptor.

       -E <entries>, --entries=<entries>
           Display this many functions.

       -f <count>, --count-filter=<count>
           Only display functions with more events than this.

       --group
           Put the counters into a counter group.

       -F <freq>, --freq=<freq>
           Profile at this frequency. Use max to use the currently maximum allowed frequency,
           i.e. the value in the kernel.perf_event_max_sample_rate sysctl.

       -i, --inherit
           Child tasks do not inherit counters.

       -k <path>, --vmlinux=<path>
           Path to vmlinux. Required for annotation functionality.

       --ignore-vmlinux
           Ignore vmlinux files.

       -m <pages>, --mmap-pages=<pages>
           Number of mmap data pages (must be a power of two) or size specification with appended
           unit character - B/K/M/G. The size is rounded up to have nearest pages power of two
           value.

       -p <pid>, --pid=<pid>
           Profile events on existing Process ID (comma separated list).

       -t <tid>, --tid=<tid>
           Profile events on existing thread ID (comma separated list).

       -u, --uid=
           Record events in threads owned by uid. Name or number.

       -r <priority>, --realtime=<priority>
           Collect data with this RT SCHED_FIFO priority.

       --sym-annotate=<symbol>
           Annotate this symbol.

       -K, --hide_kernel_symbols
           Hide kernel symbols.

       -U, --hide_user_symbols
           Hide user symbols.

       --demangle-kernel
           Demangle kernel symbols.

       -D, --dump-symtab
           Dump the symbol table used for profiling.

       -v, --verbose
           Be more verbose (show counter open errors, etc).

       -z, --zero
           Zero history across display updates.

       -s, --sort
           Sort by key(s): pid, comm, dso, symbol, parent, srcline, weight, local_weight, abort,
           in_tx, transaction, overhead, sample, period. Please see description of --sort in the
           perf-report man page.

       --fields=
           Specify output field - multiple keys can be specified in CSV format. Following fields
           are available: overhead, overhead_sys, overhead_us, overhead_children, sample and
           period. Also it can contain any sort key(s).

               By default, every sort keys not specified in --field will be appended
               automatically.

       -n, --show-nr-samples
           Show a column with the number of samples.

       --show-total-period
           Show a column with the sum of periods.

       --dsos
           Only consider symbols in these dsos. This option will affect the percentage of the
           overhead column. See --percentage for more info.

       --comms
           Only consider symbols in these comms. This option will affect the percentage of the
           overhead column. See --percentage for more info.

       --symbols
           Only consider these symbols. This option will affect the percentage of the overhead
           column. See --percentage for more info.

       -M, --disassembler-style=
           Set disassembler style for objdump.

       --source
           Interleave source code with assembly code. Enabled by default, disable with
           --no-source.

       --asm-raw
           Show raw instruction encoding of assembly instructions.

       -g
           Enables call-graph (stack chain/backtrace) recording.

       --call-graph [mode,type,min[,limit],order[,key][,branch]]
           Setup and enable call-graph (stack chain/backtrace) recording, implies -g. See
           --call-graph section in perf-record and perf-report man pages for details.

       --children
           Accumulate callchain of children to parent entry so that then can show up in the
           output. The output will have a new "Children" column and will be sorted on the data.
           It requires -g/--call-graph option enabled. See the ‘overhead calculation’ section for
           more details. Enabled by default, disable with --no-children.

       --max-stack
           Set the stack depth limit when parsing the callchain, anything beyond the specified
           depth will be ignored. This is a trade-off between information loss and faster
           processing especially for workloads that can have a very long callchain stack.

               Default: /proc/sys/kernel/perf_event_max_stack when present, 127 otherwise.

       --ignore-callees=<regex>
           Ignore callees of the function(s) matching the given regex. This has the effect of
           collecting the callers of each such function into one place in the call-graph tree.

       --percent-limit
           Do not show entries which have an overhead under that percent. (Default: 0).

       --percentage
           Determine how to display the overhead percentage of filtered entries. Filters can be
           applied by --comms, --dsos and/or --symbols options and Zoom operations on the TUI
           (thread, dso, etc).

               "relative" means it's relative to filtered entries only so that the
               sum of shown entries will be always 100%. "absolute" means it retains
               the original value before and after the filter is applied.

       -w, --column-widths=<width[,width...]>
           Force each column width to the provided list, for large terminal readability. 0 means
           no limit (default behavior).

       --proc-map-timeout
           When processing pre-existing threads /proc/XXX/mmap, it may take a long time, because
           the file may be huge. A time out is needed in such cases. This option sets the time
           out limit. The default value is 500 ms.

       -b, --branch-any
           Enable taken branch stack sampling. Any type of taken branch may be sampled. This is a
           shortcut for --branch-filter any. See --branch-filter for more infos.

       -j, --branch-filter
           Enable taken branch stack sampling. Each sample captures a series of consecutive taken
           branches. The number of branches captured with each sample depends on the underlying
           hardware, the type of branches of interest, and the executed code. It is possible to
           select the types of branches captured by enabling filters. For a full list of
           modifiers please see the perf record manpage.

               The option requires at least one branch type among any, any_call, any_ret, ind_call, cond.
               The privilege levels may be omitted, in which case, the privilege levels of the associated
               event are applied to the branch filter. Both kernel (k) and hypervisor (hv) privilege
               levels are subject to permissions.  When sampling on multiple events, branch stack sampling
               is enabled for all the sampling events. The sampled branch type is the same for all events.
               The various filters must be specified as a comma separated list: --branch-filter any_ret,u,k
               Note that this feature may not be available on all processors.

       --raw-trace
           When displaying traceevent output, do not use print fmt or plugins.

       --hierarchy
           Enable hierarchy output.

       --force
           Don’t do ownership validation.

       --num-thread-synthesize
           The number of threads to run when synthesizing events for existing processes. By
           default, the number of threads equals to the number of online CPUs.

INTERACTIVE PROMPTING KEYS

       [d]
           Display refresh delay.

       [e]
           Number of entries to display.

       [E]
           Event to display when multiple counters are active.

       [f]
           Profile display filter (>= hit count).

       [F]
           Annotation display filter (>= % of total).

       [s]
           Annotate symbol.

       [S]
           Stop annotation, return to full profile display.

       [K]
           Hide kernel symbols.

       [U]
           Hide user symbols.

       [z]
           Toggle event count zeroing across display updates.

       [qQ]
           Quit.

       Pressing any unmapped key displays a menu, and prompts for input.

OVERHEAD CALCULATION

       The overhead can be shown in two columns as Children and Self when perf collects
       callchains. The self overhead is simply calculated by adding all period values of the
       entry - usually a function (symbol). This is the value that perf shows traditionally and
       sum of all the self overhead values should be 100%.

       The children overhead is calculated by adding all period values of the child functions so
       that it can show the total overhead of the higher level functions even if they don’t
       directly execute much. Children here means functions that are called from another (parent)
       function.

       It might be confusing that the sum of all the children overhead values exceeds 100% since
       each of them is already an accumulation of self overhead of its child functions. But with
       this enabled, users can find which function has the most overhead even if samples are
       spread over the children.

       Consider the following example; there are three functions like below.

           .ft C
           void foo(void) {
               /* do something */
           }

           void bar(void) {
               /* do something */
               foo();
           }

           int main(void) {
               bar()
               return 0;
           }
           .ft

       In this case foo is a child of bar, and bar is an immediate child of main so foo also is a
       child of main. In other words, main is a parent of foo and bar, and bar is a parent of
       foo.

       Suppose all samples are recorded in foo and bar only. When it’s recorded with callchains
       the output will show something like below in the usual (self-overhead-only) output of perf
       report:

           .ft C
           Overhead  Symbol
           ........  .....................
             60.00%  foo
                     |
                     --- foo
                         bar
                         main
                         __libc_start_main

             40.00%  bar
                     |
                     --- bar
                         main
                         __libc_start_main
           .ft

       When the --children option is enabled, the self overhead values of child functions (i.e.
       foo and bar) are added to the parents to calculate the children overhead. In this case the
       report could be displayed as:

           .ft C
           Children      Self  Symbol
           ........  ........  ....................
            100.00%     0.00%  __libc_start_main
                     |
                     --- __libc_start_main

            100.00%     0.00%  main
                     |
                     --- main
                         __libc_start_main

            100.00%    40.00%  bar
                     |
                     --- bar
                         main
                         __libc_start_main

             60.00%    60.00%  foo
                     |
                     --- foo
                         bar
                         main
                         __libc_start_main
           .ft

       In the above output, the self overhead of foo (60%) was add to the children overhead of
       bar, main and __libc_start_main. Likewise, the self overhead of bar (40%) was added to the
       children overhead of main and \_\_libc_start_main.

       So \_\_libc_start_main and main are shown first since they have same (100%) children
       overhead (even though they have zero self overhead) and they are the parents of foo and
       bar.

       Since v3.16 the children overhead is shown by default and the output is sorted by its
       values. The children overhead is disabled by specifying --no-children option on the
       command line or by adding report.children = false or top.children = false in the perf
       config file.

SEE ALSO

       perf-stat(1), perf-list(1), perf-report(1)