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; 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 3.23 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/.
