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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 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 kernels).

       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 (non-portable) 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;  assign-
       ing  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.

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

       Programming for the  real  world  -  POSIX.4  by  Bill  O.  Gallmeister,  O'Reilly  &  Associates,  Inc.,  ISBN
       1-56592-074-0

COLOPHON
       This  page  is part of release 3.22 of the Linux man-pages project.  A description of the project, and informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2007-04-06          SCHED_RR_GET_INTERVAL(2)