NAME
sched_setparam,
sched_getparam,
sched_setscheduler,
sched_getscheduler,
sched_get_priority_max,
sched_get_priority_min,
sched_rr_get_interval,
sched_yield,
sched_protect,
sched_setaffinity_np,
sched_getaffinity_np —
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);
int
sched_setaffinity_np(
pid_t
pid,
size_t size,
cpuset_t *cpuset);
int
sched_getaffinity_np(
pid_t
pid,
size_t size,
cpuset_t *cpuset);
int
sched_protect(
int
priority);
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. For
SCHED_OTHER
, must be
PRI_NONE
; the kernel will dynamically assign
priorities to the thread based on CPU load.
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.
-
-
- sched_protect(priority)
- Performs priority protection using the
PTHREAD_PRIO_PROTECT
protocol. This function will
increase the protected priority of the caller thread to
priority if the current thread's protected priority
is smaller than priority. Multiple calls to
sched_protect() with a positive priority will
“push” a priority level to the current thread, whereas calling
sched_protect() with a priority
level of -1
will “pop” a priority
level. When the level reaches 0
(the same number
of “pushes” and “pops” have been issued) the
original thread priority will be restored.
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_protect(),
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.
The
sched_protect() function fails if:
-
-
- [
EINVAL
]
- The thread was not priority protected.
-
-
- [
EPERM
]
- The priority parameter was out of
range (not in the range between
SCHED_PRIO_MIN
and
SCHED_PRIO_MAX
).
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.