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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  (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.

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 3.27 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/.