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SCHED(3) Library Functions Manual SCHED(3)NAMEsched_setparam,sched_getparam,sched_setscheduler,sched_getscheduler,sched_get_priority_max,sched_get_priority_min,sched_rr_get_interval,sched_yield-- process schedulingLIBRARYPOSIX Real-time Library (librt, -lrt)SYNOPSIS#include<sched.h>intsched_setparam(pid_t pid, const struct sched_param *param); intsched_getparam(pid_t pid, struct sched_param *param); intsched_setscheduler(pid_t pid, int policy, const struct sched_param *param); intsched_getscheduler(pid_t pid); intsched_get_priority_max(int policy); intsched_get_priority_min(int policy); intsched_rr_get_interval(pid_t pid, struct timespec *interval); intsched_yield(void);DESCRIPTIONThis section describes the functions used to get scheduling information about processes, and control the scheduling of processes. 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.FUNCTIONSsched_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 calling 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 specified 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 scheduling policy specified by policy.sched_get_priority_min(policy) Returns the minimal priority which may be used for the scheduling 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 specified 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.IMPLEMENTATIONNOTESSetting CPU affinity(3) requires super-user privileges. Ordinary users can be allowed to control CPU affinity of their threads via the security.models.extensions.user_set_cpu_affinity sysctl(7). See secmodel_extensions(9). Portable applications should not use thesched_setaffinity_np() andsched_getaffinity_np() functions.RETURNVALUESsched_setparam(),sched_getparam(),sched_rr_get_interval(), andsched_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. Otherwise, -1 is returned and errno is set to indicate the error.sched_get_priority_max() andsched_get_priority_min() return the maximal/minimal priority value on success. Otherwise, -1 is returned and errno is set to indicate the error.sched_setaffinity_np() andsched_getaffinity_np() return 0 on success. Otherwise, -1 is returned and errno is set to indicate the error.ERRORSThesched_setparam() andsched_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 the PID specified by pid, and the value of pid is not zero. Thesched_getparam() andsched_getscheduler() functions fail if: [EPERM] The calling process is not a super-user and its effective user id does not match the effective user-id of the specified process. [ESRCH] No process can be found corresponding to that specified by pid, and the value of pid is not zero. Thesched_get_priority_max() andsched_get_priority_min() functions fail if: [EINVAL] The specified scheduling policy is invalid. Thesched_rr_get_interval() function fails if: [ESRCH] No process can be found corresponding to that specified by pid, and the value of pid is not zero.SEEALSOaffinity(3), cpuset(3), pset(3), schedctl(8)STANDARDSThese functions, exceptsched_setaffinity_np() andsched_getaffinity_np(), are expected to conform the IEEE Std 1003.1-2001 (``POSIX.1'') standard.HISTORYThe scheduling functions appeared in NetBSD 5.0. NetBSD 7.1.2 December 4, 2011 NetBSD 7.1.2