Open Source Software

chrt(1)



NAME

   chrt - manipulate the real-time attributes of a process

SYNOPSIS

   chrt [options] priority command [argument...]
   chrt [options] -p [priority] pid

DESCRIPTION

   chrt  sets  or  retrieves  the  real-time  scheduling  attributes of an
   existing pid, or runs command with the given attributes.

POLICIES

   -o, --other
          Set scheduling policy to SCHED_OTHER.  This is the default Linux
          scheduling policy.

   -f, --fifo
          Set scheduling policy to SCHED_FIFO.

   -r, --rr
          Set  scheduling  policy to SCHED_RR.  When no policy is defined,
          the SCHED_RR is used as the default.

   -b, --batch
          Set scheduling policy to SCHED_BATCH (Linux-specific,  supported
          since 2.6.16).  The priority argument has to be set to zero.

   -i, --idle
          Set  scheduling  policy to SCHED_IDLE (Linux-specific, supported
          since 2.6.23).  The priority argument has to be set to zero.

   -d, --deadline
          Set  scheduling  policy   to   SCHED_DEADLINE   (Linux-specific,
          supported  since  3.14).  The priority argument has to be set to
          zero.    See   also   --sched-runtime,   --sched-deadline    and
          --sched-period.   The  relation  between the options required by
          the kernel is runtime <= deadline <= period.  chrt copies period
          to deadline if --sched-deadline is not specified and deadline to
          runtime if --sched-runtime is not specified.  It means  that  at
          least --sched-period has to be specified.  See sched(7) for more
          details.

SCHEDULING OPTIONS

   -T, --sched-runtime nanoseconds
          Specifies runtime parameter for  SCHED_DEADLINE  policy  (Linux-
          specific).

   -P, --sched-period nanoseconds
          Specifies  period  parameter  for  SCHED_DEADLINE policy (Linux-
          specific).

   -D, --sched-deadline nanoseconds
          Specifies deadline parameter for SCHED_DEADLINE  policy  (Linux-
          specific).

   -R, --reset-on-fork
          Add  SCHED_RESET_ON_FORK  flag  to  the  SCHED_FIFO  or SCHED_RR
          scheduling policy (Linux-specific, supported since 2.6.31).

OPTIONS

   -a, --all-tasks
          Set or retrieve the  scheduling  attributes  of  all  the  tasks
          (threads) for a given PID.

   -m, --max
          Show minimum and maximum valid priorities, then exit.

   -p, --pid
          Operate on an existing PID and do not launch a new task.

   -v, --verbose
          Show status information.

   -V, --version
          Display version information and exit.

   -h, --help
          Display help text and exit.

USAGE

   The default behavior is to run a new command:
          chrt priority command [arguments]

   You can also retrieve the real-time attributes of an existing task:
          chrt -p pid

   Or set them:
          chrt -r -p priority pid

PERMISSIONS

   A user must possess CAP_SYS_NICE to change the scheduling attributes of
   a process.  Any user can retrieve the scheduling information.

NOTES

   Only SCHED_FIFO, SCHED_OTHER and SCHED_RR are  part  of  POSIX  1003.1b
   Process  Scheduling.  The other scheduling attributes may be ignored on
   some systems.

   Linux' default scheduling policy is SCHED_OTHER.

SEE ALSO

   taskset(1), nice(1), renice(1), sched(7)

   See sched_setscheduler(2) for a description  of  the  Linux  scheduling
   scheme.

AUTHORS

   Robert Love rml@tech9.net
   Karel Zak kzak@redhat.com

AVAILABILITY

   The  chrt  command  is  part of the util-linux package and is available
   from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.



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