sched_rr_get_interval

SCHED_RR_GET_INTERVAL(2)    Linux Programmer's Manual   SCHED_RR_GET_INTERVAL(2)



NAME
       sched_rr_get_interval - get the SCHED_RR interval for the named process

SYNOPSIS
       #include <sched.h>

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

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

ERRORS
       EFAULT Problem with copying information to user space.

       EINVAL Invalid pid.

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

       ESRCH  Could not find a process with the ID pid.

CONFORMING TO
       POSIX.1-2001, POSIX.1-2008.

NOTES
       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 2.6.24.

       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
       sched(7)

COLOPHON
       This page is part of release 5.12 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.



Linux                              2021-03-22           SCHED_RR_GET_INTERVAL(2)