linuXperts.org

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_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 ker- nels). 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 quan- tum 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 Linux 2007-04-06 SCHED_RR_GET_INTERVAL(2)