sched_getscheduler(3) Library Functions Manual sched_getscheduler(3)NAME
sched_getscheduler - Returns the scheduling policy of a process (P1003.1b)
LIBRARY
Realtime Library (librt.so, librt.a)
SYNOPSIS
#include <sched.h>
int sched_getscheduler (
pid_t pid);
PARAMETERS
pid Specifies the ID of the process for which the scheduling policy is to be obtained. If pid is zero, the scheduling policy of the
calling process is obtained.
DESCRIPTION
The sched_getscheduler function returns the current scheduling policy of a process. The values that can be returned are defined in the
header file <sched.h>.
The sched_setscheduler function changes the scheduling policy and priority of a process. Changing the scheduling policy and priority
ensures that an application can determine more effectively when a process will run.
The realtime scheduling policies are as follows:
SCHED_FIFO Specifies the first-in, first-out (FIFO) scheduling policy
SCHED_RR Specifies the round-robin (RR) scheduling policy
SCHED_OTHER Specifies the standard timesharing scheduling policy
The SCHED_FIFO and SCHED_RR scheduling policies are fixed-priority scheduling policies. You can specify a priority for your process and the
scheduler will not adjust it. Setting priorities in conjunction with a SCHED_FIFO scheduling policy allows a critical process to run as
soon as it is ready, for as long as it needs to run, because the process will preempt other lower-priority processes.
The round-robin scheduling policy is similar to first in-first out, but also imposes a quantum on execution time. Use the
sched_rr_get_interval function to determine the current quantum for process execution under the SCHED_RR scheduling policy.
The scheduler adjusts process priorities running under the timesharing scheduling policy.
No special privileges are needed to use the sched_getscheduler function.
RETURN VALUES
On a successful call to sched_getscheduler, the scheduling policy of the process is returned. If there is an error, -1 is returned and
errno is set to indicate the error.
ERRORS
The sched_getscheduler function fails under the following condition:
[ESRCH] No process can be found corresponding to that specified by pid.
RELATED INFORMATION
Functions: getpid(2), sched_getparam(3), sched_setparam(3), sched_setscheduler(3)
Guide to Realtime Programming delim off
sched_getscheduler(3)
Check Out this Related Man Page
SCHED(3) BSD 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 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.
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 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.
IMPLEMENTATION NOTES
Setting 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 the sched_setaffinity_np() and sched_getaffinity_np() functions.
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. Otherwise, -1 is returned and errno is set to indicate the error.
sched_get_priority_max() and sched_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() and sched_getaffinity_np() return 0 on success. 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 the PID specified by pid, and the 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 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.
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 specified by pid, and the value of pid is not zero.
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.
BSD December 4, 2011 BSD