Provided by: schedtool_1.3.0-1_amd64 bug


       schedtool - query and set CPU scheduling parameters


              [-0|-N] [-1|-F] [-2|-R] [-3|-B] [-4|-I] [-5|-D]
              [-M policy]
              [-a affinity]
              [-p prio]
              [-n nice_level]
              [-e command [arg ...]]
              [LIST OF PIDs]


       schedtool can set all CPU scheduling parameters Linux is capable of or display information
       for given processes.

       Long-running, non-interactive tasks may benefit from SCHED_BATCH as timeslices are longer,
       less  system-time  is  wasted  by  computing the next runnable process and the caches stay

       Audio/video or other near-realtime applications may run  with  less  skipping  if  set  to
       SCHED_RR.  Use the static priority-switch -p to designate inter-process-hierarchies.

       schedtool now supports setting the CPU-affinity introduced in linux 2.5.8.


       -N or -0
              set all PIDs to SCHED_NORMAL/OTHER

       -F or -1
              to SCHED_FIFO   root-credentials required

       -R or -2
              to SCHED_RR     root-credentials required

       -B or -3
              to SCHED_BATCH

       -I or -4
              to SCHED_ISO

       -D or -5
              to SCHED_IDLEPRIO

       -M policy
              for  manual/raw  mode; policy is the number of the scheduling policy (see above for
              0-4).  This option  is  mostly  for  kernel  guys  that  want  to  test  their  new

       -p prio
              specify  static  priority required for SCHED_FIFO and SCHED_RR. Usually ranged from

       -a affinity
              set the PID's affinity to this bitmask (hexadecimal); alternatively, a list mode is

       -n nice_level
              set the PID's nice level; see nice(2), nice(1).

       -e command [arg ...]
              execute  command  with  given scheduling parameters (overwrites schedtool's process
              image). See EXAMPLES.

       -r     display min and max priority for each policy.

       -v     be verbose.

       -h     help


       To query the $SHELL's policies:

           #> schedtool $$

       To query some PIDs, namely 1 2 and 3:

           #> schedtool 1 2 3

       To execute mplayer in SCHED_RR with priority 20. The  priority  arg  is  needed  for  both

           #> schedtool -R -p 20 -e mplayer -quiet some_file.avi

       To set current shell to SCHED_BATCH, which all programs the shell starts will inherit:

           #> schedtool -3 $$

       To set all processes with the name 'cpu_hog' to SCHED_BATCH:

           #> schedtool -3 `pidof cpu_hog`

       To set a process' affinity to only the first CPU (CPU0):

           #> schedtool -a 0x1 <PID>

       Using the list mode and affinty of CPU0 and CPU3:

           #> schedtool -a 0,3 <PID>

       A combination of an affinity and a policy-argument is - of course - always possible.

          #> schedtool -B -a 0x1 <PID>


       The affinity-argument determines on which CPUs a process is allowed to run. It consists of
       a simple bitmask represented in hexadecimal.  CPU0 is  denoted  by  the  least-significant
       bit, CPU1 by the second least-significant and so on, thus giving:

           0x1 -> only run on CPU0

           0x2 -> only run on CPU1

           0x4 -> only run on CPU2

           0x8 -> only run on CPU3 ... and so on.

       Multi-target CPUs may be specified using bitwise OR of the values:

           0x7 -> run on CPUs 0, 1, 2 but NOT on 4

           0x3 -> run only on CPUs 0 and 1

       The default is to run a process on all CPUs, giving a mask of

           0xf for all 4 CPUs

           0xff for all 8 CPUs


       Alternatively  a  list  mode is supported where you can specify the CPUs delimited by ",".
       The following runs <PID> on CPU0 and CPU1 (equivalent to 0x3):

          #> schedtool -a 0,1 <PID>


       SCHED_NORMAL / SCHED_OTHER This is the default policy and for  the  average  program  with
       some interaction. Does preemption of other processes.

       SCHED_FIFO  First-In,  First Out Scheduler, used only for real-time contraints.  Processes
       in this class are usually not preempted by others, they need to free themselves  from  the
       CPU via sched_yield() and as such you need special designed applications. Use with extreme
       care.  ROOT-credentials required.

       SCHED_RR Round-Robin Scheduler, also used for real-time constraints. CPU-time is  assigned
       in  an  round-robin  fashion  with  a  much  smaller  timeslice than with SCHED_NORMAL and
       processes  in  this  group  are  favoured  over  SCHED_NORMAL.  Usable   for   audio/video
       applications near peak rate of the system.  ROOT-credentials required.

       SCHED_BATCH  [  since  2.6.16  in mainline ] SCHED_BATCH was designed for non-interactive,
       CPU-bound applications.  It uses longer timeslices (to better exploit the cache), but  can
       be  interrupted anytime by other processes in other classes to guaratee interaction of the
       system. Processes in this class are selected last but may result in a considerable  speed-
       up (up to 300%). No interactive boosting is done.

       SCHED_ISO  [ patch needed ] SCHED_ISO was designed to give users a SCHED_RR-similar class.
       To quote Con Kolivas: "This is a non-expiring scheduler policy  designed  to  guarantee  a
       timeslice within a reasonable latency while preventing starvation.  Good for gaming, video
       at the limits of hardware, video capture etc."

       SCHED_IDLEPRIO [ patch  needed  ]  SCHED_IDLEPRIO  is  similar  to  SCHED_BATCH,  but  was
       explicitely  designed to consume only the time the CPU is idle. No interactive boosting is
       done.  If you used SCHED_BATCH in the -ck kernels this is what you want since 2.6.16


       PID 0 means "current process", in our case, schedtool. May occur when using the -e switch.

       Be careful with SCHED_FIFO! You may lock out other processes from the CPU, including  your

       For SCHED_BATCH you certainly need the a recent 2.6 kernel.

       A  short  overview  is given in SCHED_DESIGN and the README contains thourough discussion.
       The INSTALL file also lists all prerequisites and where you can get patches.

       Affinity 0x0 should never be used.


       sched_setscheduler(2), sched_setaffinity(2), nice(2), nice(1), renice(3).


       You need some knowledge about the kernel and scheduling. The author  is  a  grumpy  little



       Please      contact      me      via's     "contact     author"-feature

                                         1 November 2006                             SCHEDTOOL(8)