sched(3) - NetBSD Manual Pages

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SCHED(3)                NetBSD Library Functions Manual               SCHED(3)


NAME

     sched_setparam, sched_getparam, sched_setscheduler, sched_getscheduler,
     sched_get_priority_max, sched_get_priority_min, sched_rr_get_interval,
     sched_yield -- process scheduling


LIBRARY

     POSIX Real-time Library (librt, -lrt)


SYNOPSIS

     #include <sched.h>

     int
     sched_setparam(pid_t pid, const struct sched_param *param);

     int
     sched_getparam(pid_t pid, struct sched_param *param);

     int
     sched_setscheduler(pid_t pid, int policy,
         const struct sched_param *param);

     int
     sched_getscheduler(pid_t pid);

     int
     sched_get_priority_max(int policy);

     int
     sched_get_priority_min(int policy);

     int
     sched_rr_get_interval(pid_t pid, struct timespec *interval);

     int
     sched_yield(void);


DESCRIPTION

     This section describes the functions used to get the scheduling informa-
     tion about the processes, and control the scheduling of the process.

     Available scheduling policies (classes) are:

     SCHED_OTHER  Time-sharing (TS) scheduling policy.  The default policy in
                  NetBSD.

     SCHED_FIFO   First in, first out (FIFO) scheduling policy.

     SCHED_RR     Round robin scheduling policy.

     The struct sched_param contains at least one member:

     sched_priority
            Specifies the priority of the process.


FUNCTIONS

     sched_setparam(pid, param)
              Sets the scheduling parameters for the process specified by pid
              to param.  If the value of pid is equal to zero, then the call-
              ing process is used.

     sched_getparam(pid, param)
              Gets the scheduling parameters of the process specified by pid
              into the structure param.  If the value of pid is equal to zero,
              then the calling process is used.

     sched_setscheduler(pid, policy, param)
              Set the scheduling policy and parameters for the process speci-
              fied by pid.  If the value of pid is equal to zero, then the
              calling process is used.

     sched_getscheduler(pid)
              Returns the scheduling policy of the process specified by pid.
              If the value of pid is equal to zero, then the calling process
              is used.

     sched_get_priority_max(policy)
              Returns the maximal priority which may be used for the schedul-
              ing policy specified by policy.

     sched_get_priority_min(policy)
              Returns the minimal priority which may be used for the schedul-
              ing policy specified by policy.

     sched_rr_get_interval(pid, interval)
              Returns the time quantum into the structure interval of the
              process specified by pid.  If the value of pid is equal to zero,
              then the calling process is used.  The process must be running
              at SCHED_RR scheduling policy.

     sched_yield()
              Yields a processor voluntarily and gives other threads a chance
              to run without waiting for an involuntary preemptive switch.

     sched_setaffinity_np(pid, size, cpuset)
              Set the affinity mask specified by cpuset for the process speci-
              fied by pid.  At least one valid CPU must be set in the mask.

     sched_getaffinity_np(pid, size, cpuset)
              Get the affinity mask of the process specified by pid into the
              cpuset.


RETURN VALUES

     sched_setparam(), sched_getparam(), sched_rr_get_interval(), and
     sched_yield() return 0 on success.  Otherwise, -1 is returned and errno
     is set to indicate the error.

     sched_setscheduler() returns the previously used scheduling policy on
     success.  Otherwise, -1 is returned and errno is set to indicate the
     error.

     sched_getscheduler() returns the scheduling policy on success.  Other-
     wise, -1 is returned and errno is set to indicate the error.

     The sched_get_priority_max() and sched_get_priority_min() return the max-
     imal/minimal priority value on success.  Otherwise, -1 is returned and
     errno is set to indicate the error.

     The sched_setaffinity_np() and sched_getaffinity_np() return 0 on suc-
     cess.  Otherwise, -1 is returned and errno is set to indicate the error.


ERRORS

     The sched_setparam() and sched_setscheduler() functions fail if:

     [EINVAL]           At least one of the specified scheduling parameters
                        was invalid.

     [EPERM]            The calling process has no appropriate privileges to
                        perform the operation.

     [ESRCH]            No process can be found corresponding to that speci-
                        fied by pid, and value of pid is not zero.

     The sched_getparam() and sched_getscheduler() functions fail if:

     [EPERM]            The calling process is not a super-user and its effec-
                        tive user id does not match the effective user-id of
                        the specified process.

     [ESRCH]            No process can be found corresponding to that speci-
                        fied by pid, and value of pid is not zero.

     The sched_get_priority_max() and sched_get_priority_min() functions fail
     if:

     [EINVAL]           The specified scheduling policy is invalid.

     The sched_rr_get_interval() function fails if:

     [ESRCH]            No process can be found corresponding to that speci-
                        fied by pid, and value of pid is not zero.


NOTES

     Portable applications should not use sched_setaffinity_np() and
     sched_getaffinity_np() functions.


SEE ALSO

     affinity(3), cpuset(3), pset(3), schedctl(8)


STANDARDS

     These functions, except sched_setaffinity_np() and
     sched_getaffinity_np(), are expected to conform the IEEE Std 1003.1-2001
     (``POSIX.1'') standard.


HISTORY

     The scheduling functions appeared in NetBSD 5.0.

NetBSD 5.0.1                   October 31, 2008                   NetBSD 5.0.1