1SCHED_RR_GET_INTERVAL(2)   Linux Programmer's Manual  SCHED_RR_GET_INTERVAL(2)
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NAME

6       sched_rr_get_interval - get the SCHED_RR interval for the named process
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SYNOPSIS

9       #include <sched.h>
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11       int sched_rr_get_interval(pid_t pid, struct timespec * tp);
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DESCRIPTION

14       sched_rr_get_interval()  writes  into the timespec structure pointed to
15       by tp the round-robin time quantum for the process identified by pid.
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17       The timespec structure has the following form:
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19           struct timespec {
20               time_t tv_sec;    /* seconds */
21               long   tv_nsec;   /* nanoseconds */
22           };
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24       If pid is zero, the time quantum for the  calling  process  is  written
25       into  *tp.  The identified process should be running under the SCHED_RR
26       scheduling policy.  POSIX systems on which  sched_rr_get_interval()  is
27       available define _POSIX_PRIORITY_SCHEDULING in <unistd.h>.
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RETURN VALUE

30       On  success,  sched_rr_get_interval()  returns  0.   On  error,  -1  is
31       returned, and errno is set appropriately.
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ERRORS

34       EFAULT Problem with copying information to userspace.
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36       EINVAL Invalid pid.
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38       ENOSYS The system call is not yet implemented (only on rather old  ker‐
39              nels).
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41       ESRCH  The process whose ID is pid could not be found.
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CONFORMING TO

44       POSIX.1-2001.
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NOTES

47   Linux Notes
48       POSIX  does  not  specify any mechanism for controlling the size of the
49       round-robin time quantum.   However,  Linux  provides  a  (nonportable)
50       method  of  doing this.  The quantum can be controlled by adjusting the
51       process's nice value (see setpriority(2)).  Assigning a negative (i.e.,
52       high)  nice  value  results  in  a longer quantum; assigning a positive
53       (i.e., low) nice value results in a shorter quantum.  The default quan‐
54       tum is 0.1 seconds; the degree to which changing the nice value affects
55       the quantum has varied somewhat across kernel versions.
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SEE ALSO

58       sched_setscheduler(2) has a description of the Linux scheduling scheme.
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60       Programming for the real  world  -  POSIX.4  by  Bill  O.  Gallmeister,
61       O'Reilly & Associates, Inc., ISBN 1-56592-074-0
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COLOPHON

64       This  page  is  part of release 3.25 of the Linux man-pages project.  A
65       description of the project, and information about reporting  bugs,  can
66       be found at http://www.kernel.org/doc/man-pages/.
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70Linux                             2007-04-06          SCHED_RR_GET_INTERVAL(2)
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