sched_rr_get_interval(2) — Linux manual page



NAME         top

       sched_rr_get_interval - get the SCHED_RR interval for the named

SYNOPSIS         top

       #include <sched.h>

       int sched_rr_get_interval(pid_t pid, struct timespec *tp);

DESCRIPTION         top

       sched_rr_get_interval() writes into the timespec structure
       pointed to by tp the round-robin time quantum for the process
       identified by pid.  The specified process should be running under
       the SCHED_RR scheduling policy.

       The timespec structure has the following form:

           struct timespec {
               time_t tv_sec;    /* seconds */
               long   tv_nsec;   /* nanoseconds */

       If pid is zero, the time quantum for the calling process is
       written into *tp.

RETURN VALUE         top

       On success, sched_rr_get_interval() returns 0.  On error, -1 is
       returned, and errno is set to indicate the error.

ERRORS         top

       EFAULT Problem with copying information to user space.

       EINVAL Invalid pid.

       ENOSYS The system call is not yet implemented (only on rather old

       ESRCH  Could not find a process with the ID pid.

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008.

NOTES         top

       POSIX systems on which sched_rr_get_interval() is available
       define _POSIX_PRIORITY_SCHEDULING in <unistd.h>.

   Linux notes
       POSIX does not specify any mechanism for controlling the size of
       the round-robin time quantum.  Older Linux kernels provide a
       (nonportable) method of doing this.  The quantum can be
       controlled by adjusting the process's nice value (see
       setpriority(2)).  Assigning a negative (i.e., high) nice value
       results in a longer quantum; assigning a positive (i.e., low)
       nice value results in a shorter quantum.  The default quantum is
       0.1 seconds; the degree to which changing the nice value affects
       the quantum has varied somewhat across kernel versions.  This
       method of adjusting the quantum was removed starting with Linux

       Linux 3.9 added a new mechanism for adjusting (and viewing) the
       SCHED_RR quantum: the /proc/sys/kernel/sched_rr_timeslice_ms file
       exposes the quantum as a millisecond value, whose default is 100.
       Writing 0 to this file resets the quantum to the default value.

SEE ALSO         top


COLOPHON         top

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Linux                          2021-03-22       SCHED_RR_GET_INTERVAL(2)

Pages that refer to this page: sched_setattr(2)sched_setscheduler(2)syscalls(2)proc(5)sched(7)