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_PRIOR-
       ITY_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
       (nonportable)  method  of doing this.  The quantum can be controlled by adjusting the process's nice value (see setprior-
       ity(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.

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 3.25 of the Linux man-pages project.  A description of the project,  and  information  about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                                                      2007-04-06                                   SCHED_RR_GET_INTERVAL(2)