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 appropriately.

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 5.03 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                             2017-09-15          SCHED_RR_GET_INTERVAL(2)