Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

Linux 2.6 - man page for sched_rr_get_interval (linux section 2)

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

sched_rr_get_interval - get the SCHED_RR interval for the named process
#include <sched.h> int sched_rr_get_interval(pid_t pid, struct timespec * tp);
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>.
On success, sched_rr_get_interval() returns 0. On error, -1 is returned, and errno is set appropriately.
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.
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.
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
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 Linux 2007-04-06 SCHED_RR_GET_INTERVAL(2)