sched_rr_get_interval


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 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.  The identified process should be running under the SCHED_RR
       scheduling policy.  POSIX systems on which  sched_rr_get_interval()  is
       available define _POSIX_PRIORITY_SCHEDULING in <unistd.h>.

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 userspace.

       EINVAL Invalid pid.

       ENOSYS The system call is not yet implemented (only on rather old  ker-
              nels).

       ESRCH  The process whose ID is pid could not be found.

CONFORMING TO
       POSIX.1-2001.

NOTES
   Linux Notes
       POSIX  does  not  specify any mechanism for controlling the size of the
       round-robin time quantum.   However,  Linux  provides  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 quan-
       tum is 0.1 seconds; the degree to which changing the nice value affects
       the quantum has varied somewhat across kernel versions.

SEE ALSO
       sched_setscheduler(2) has a description of the Linux scheduling scheme.

       Programming for the real  world  -  POSIX.4  by  Bill  O.  Gallmeister,
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