NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

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

NAME         top

       sched_rr_get_interval  -  get  the  SCHED_RR  interval  for the named
       process

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 appropriately.

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
              kernels).

       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 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         top

       sched(7)

COLOPHON         top

       This page is part of release 4.08 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                            2015-08-08         SCHED_RR_GET_INTERVAL(2)