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SCHED(7) Linux Programmer's Manual SCHED(7)

NAME
sched - overview of CPU scheduling

DESCRIPTION
Since Linux 2.6.23, the default scheduler is CFS, the "Completely Fair Scheduler". The CFS
scheduler replaced the earlier "O(1)" scheduler.

API summary
Linux provides the following system calls for controlling the CPU scheduling behavior, pol‐
icy, and priority of processes (or, more precisely, threads).

nice(2)
Set a new nice value for the calling thread, and return the new nice value.

getpriority(2)
Return the nice value of a thread, a process group, or the set of threads owned by a
specified user.

setpriority(2)
Set the nice value of a thread, a process group, or the set of threads owned by a
specified user.

sched_setscheduler(2)
Set the scheduling policy and parameters of a specified thread.

sched_getscheduler(2)
Return the scheduling policy of a specified thread.

sched_setparam(2)
Set the scheduling parameters of a specified thread.

sched_getparam(2)
Fetch the scheduling parameters of a specified thread.

sched_get_priority_max(2)
Return the maximum priority available in a specified scheduling policy.

sched_get_priority_min(2)
Return the minimum priority available in a specified scheduling policy.

sched_rr_get_interval(2)
Fetch the quantum used for threads that are scheduled under the "round-robin" schedul‐
ing policy.

sched_yield(2)
Cause the caller to relinquish the CPU, so that some other thread be executed.

sched_setaffinity(2)
(Linux-specific) Set the CPU affinity of a specified thread.

sched_getaffinity(2)
(Linux-specific) Get the CPU affinity of a specified thread.

sched_setattr(2)
Set the scheduling policy and parameters of a specified thread. This (Linux-specific)
system call provides a superset of the functionality of sched_setscheduler(2) and
sched_setparam(2).

sched_getattr(2)
Fetch the scheduling policy and parameters of a specified thread. This (Linux-spe‐
cific) system call provides a superset of the functionality of sched_getscheduler(2)
and sched_getparam(2).

Scheduling policies
The scheduler is the kernel component that decides which runnable thread will be executed by
the CPU next. Each thread has an associated scheduling policy and a static scheduling prior‐
ity, sched_priority. The scheduler makes its decisions based on knowledge of the scheduling
policy and static priority of all threads on the system.

For threads scheduled under one of the normal scheduling policies (SCHED_OTHER, SCHED_IDLE,
SCHED_BATCH), sched_priority is not used in scheduling decisions (it must be specified as 0).

Processes scheduled under one of the real-time policies (SCHED_FIFO, SCHED_RR) have a
sched_priority value in the range 1 (low) to 99 (high). (As the numbers imply, real-time
threads always have higher priority than normal threads.) Note well: POSIX.1 requires an im‐
plementation to support only a minimum 32 distinct priority levels for the real-time poli‐
cies, and some systems supply just this minimum. Portable programs should use sched_get_pri‐‐
ority_min(2) and sched_get_priority_max(2) to find the range of priorities supported for a
particular policy.

Conceptually, the scheduler maintains a list of runnable threads for each possible sched_pri‐
ority value. In order to determine which thread runs next, the scheduler looks for the
nonempty list with the highest static priority and selects the thread at the head of this
list.

A thread's scheduling policy determines where it will be inserted into the list of threads
with equal static priority and how it will move inside this list.

All scheduling is preemptive: if a thread with a higher static priority becomes ready to run,
the currently running thread will be preempted and returned to the wait list for its static
priority level. The scheduling policy determines the ordering only within the list of
runnable threads with equal static priority.

SCHED_FIFO: First in-first out scheduling
SCHED_FIFO can be used only with static priorities higher than 0, which means that when a
SCHED_FIFO thread becomes runnable, it will always immediately preempt any currently running
SCHED_OTHER, SCHED_BATCH, or SCHED_IDLE thread. SCHED_FIFO is a simple scheduling algorithm
without time slicing. For threads scheduled under the SCHED_FIFO policy, the following rules
apply:

1) A running SCHED_FIFO thread that has been preempted by another thread of higher priority
will stay at the head of the list for its priority and will resume execution as soon as
all threads of higher priority are blocked again.

2) When a blocked SCHED_FIFO thread becomes runnable, it will be inserted at the end of the
list for its priority.

3) If a call to sched_setscheduler(2), sched_setparam(2), sched_setattr(2), pthread_setsched‐‐
param(3), or pthread_setschedprio(3) changes the priority of the running or runnable
SCHED_FIFO thread identified by pid the effect on the thread's position in the list de‐
pends on the direction of the change to threads priority:

• If the thread's priority is raised, it is placed at the end of the list for its new
priority. As a consequence, it may preempt a currently running thread with the same
priority.

• If the thread's priority is unchanged, its position in the run list is unchanged.

• If the thread's priority is lowered, it is placed at the front of the list for its new
priority.

According to POSIX.1-2008, changes to a thread's priority (or policy) using any mechanism
other than pthread_setschedprio(3) should result in the thread being placed at the end of
the list for its priority.

4) A thread calling sched_yield(2) will be put at the end of the list.

No other events will move a thread scheduled under the SCHED_FIFO policy in the wait list of
runnable threads with equal static priority.

A SCHED_FIFO thread runs until either it is blocked by an I/O request, it is preempted by a
higher priority thread, or it calls sched_yield(2).

SCHED_RR: Round-robin scheduling
SCHED_RR is a simple enhancement of SCHED_FIFO. Everything described above for SCHED_FIFO
also applies to SCHED_RR, except that each thread is allowed to run only for a maximum time
quantum. If a SCHED_RR thread has been running for a time period equal to or longer than the
time quantum, it will be put at the end of the list for its priority. A SCHED_RR thread that
has been preempted by a higher priority thread and subsequently resumes execution as a run‐
ning thread will complete the unexpired portion of its round-robin time quantum. The length
of the time quantum can be retrieved using sched_rr_get_interval(2).

SCHED_DEADLINE: Sporadic task model deadline scheduling
Since version 3.14, Linux provides a deadline scheduling policy (SCHED_DEADLINE). This pol‐
icy is currently implemented using GEDF (Global Earliest Deadline First) in conjunction with
CBS (Constant Bandwidth Server). To set and fetch this policy and associated attributes, one
must use the Linux-specific sched_setattr(2) and sched_getattr(2) system calls.

A sporadic task is one that has a sequence of jobs, where each job is activated at most once
per period. Each job also has a relative deadline, before which it should finish execution,
and a computation time, which is the CPU time necessary for executing the job. The moment
when a task wakes up because a new job has to be executed is called the arrival time (also
referred to as the request time or release time). The start time is the time at which a task
starts its execution. The absolute deadline is thus obtained by adding the relative deadline
to the arrival time.

The following diagram clarifies these terms:

When setting a SCHED_DEADLINE policy for a thread using sched_setattr(2), one can specify
three parameters: Runtime, Deadline, and Period. These parameters do not necessarily corre‐
spond to the aforementioned terms: usual practice is to set Runtime to something bigger than
the average computation time (or worst-case execution time for hard real-time tasks), Dead‐
line to the relative deadline, and Period to the period of the task. Thus, for SCHED_DEAD‐‐
LINE scheduling, we have:

The three deadline-scheduling parameters correspond to the sched_runtime, sched_deadline, and
sched_period fields of the sched_attr structure; see sched_setattr(2). These fields express
values in nanoseconds. If sched_period is specified as 0, then it is made the same as
sched_deadline.

The kernel requires that:

sched_runtime <= sched_deadline <= sched_period

In addition, under the current implementation, all of the parameter values must be at least
1024 (i.e., just over one microsecond, which is the resolution of the implementation), and
less than 2^63. If any of these checks fails, sched_setattr(2) fails with the error EINVAL.

The CBS guarantees non-interference between tasks, by throttling threads that attempt to
over-run their specified Runtime.

To ensure deadline scheduling guarantees, the kernel must prevent situations where the set of
SCHED_DEADLINE threads is not feasible (schedulable) within the given constraints. The ker‐
nel thus performs an admittance test when setting or changing SCHED_DEADLINE policy and at‐
tributes. This admission test calculates whether the change is feasible; if it is not,
sched_setattr(2) fails with the error EBUSY.

For example, it is required (but not necessarily sufficient) for the total utilization to be
less than or equal to the total number of CPUs available, where, since each thread can maxi‐
mally run for Runtime per Period, that thread's utilization is its Runtime divided by its Pe‐
riod.

In order to fulfill the guarantees that are made when a thread is admitted to the SCHED_DEAD‐‐
LINE policy, SCHED_DEADLINE threads are the highest priority (user controllable) threads in
the system; if any SCHED_DEADLINE thread is runnable, it will preempt any thread scheduled
under one of the other policies.

A call to fork(2) by a thread scheduled under the SCHED_DEADLINE policy fails with the error
EAGAIN, unless the thread has its reset-on-fork flag set (see below).

A SCHED_DEADLINE thread that calls sched_yield(2) will yield the current job and wait for a
new period to begin.

SCHED_OTHER: Default Linux time-sharing scheduling
SCHED_OTHER can be used at only static priority 0 (i.e., threads under real-time policies al‐
ways have priority over SCHED_OTHER processes). SCHED_OTHER is the standard Linux time-shar‐
ing scheduler that is intended for all threads that do not require the special real-time
mechanisms.

The thread to run is chosen from the static priority 0 list based on a dynamic priority that
is determined only inside this list. The dynamic priority is based on the nice value (see
below) and is increased for each time quantum the thread is ready to run, but denied to run
by the scheduler. This ensures fair progress among all SCHED_OTHER threads.

In the Linux kernel source code, the SCHED_OTHER policy is actually named SCHED_NORMAL.

The nice value
The nice value is an attribute that can be used to influence the CPU scheduler to favor or
disfavor a process in scheduling decisions. It affects the scheduling of SCHED_OTHER and
SCHED_BATCH (see below) processes. The nice value can be modified using nice(2), setprior‐‐
ity(2), or sched_setattr(2).

According to POSIX.1, the nice value is a per-process attribute; that is, the threads in a
process should share a nice value. However, on Linux, the nice value is a per-thread attri‐
bute: different threads in the same process may have different nice values.

The range of the nice value varies across UNIX systems. On modern Linux, the range is -20
(high priority) to +19 (low priority). On some other systems, the range is -20..20. Very
early Linux kernels (Before Linux 2.0) had the range -infinity..15.

The degree to which the nice value affects the relative scheduling of SCHED_OTHER processes
likewise varies across UNIX systems and across Linux kernel versions.

With the advent of the CFS scheduler in kernel 2.6.23, Linux adopted an algorithm that causes
relative differences in nice values to have a much stronger effect. In the current implemen‐
tation, each unit of difference in the nice values of two processes results in a factor of
1.25 in the degree to which the scheduler favors the higher priority process. This causes
very low nice values (+19) to truly provide little CPU to a process whenever there is any
other higher priority load on the system, and makes high nice values (-20) deliver most of
the CPU to applications that require it (e.g., some audio applications).

On Linux, the RLIMIT_NICE resource limit can be used to define a limit to which an unprivi‐
leged process's nice value can be raised; see setrlimit(2) for details.

For further details on the nice value, see the subsections on the autogroup feature and group
scheduling, below.

SCHED_BATCH: Scheduling batch processes
(Since Linux 2.6.16.) SCHED_BATCH can be used only at static priority 0. This policy is
similar to SCHED_OTHER in that it schedules the thread according to its dynamic priority
(based on the nice value). The difference is that this policy will cause the scheduler to
always assume that the thread is CPU-intensive. Consequently, the scheduler will apply a
small scheduling penalty with respect to wakeup behavior, so that this thread is mildly dis‐
favored in scheduling decisions.

This policy is useful for workloads that are noninteractive, but do not want to lower their
nice value, and for workloads that want a deterministic scheduling policy without interactiv‐
ity causing extra preemptions (between the workload's tasks).

SCHED_IDLE: Scheduling very low priority jobs
(Since Linux 2.6.23.) SCHED_IDLE can be used only at static priority 0; the process nice
value has no influence for this policy.

This policy is intended for running jobs at extremely low priority (lower even than a +19
nice value with the SCHED_OTHER or SCHED_BATCH policies).

Resetting scheduling policy for child processes
Each thread has a reset-on-fork scheduling flag. When this flag is set, children created by
fork(2) do not inherit privileged scheduling policies. The reset-on-fork flag can be set by
either:

* ORing the SCHED_RESET_ON_FORK flag into the policy argument when calling sched_setsched‐‐
uler(2) (since Linux 2.6.32); or

* specifying the SCHED_FLAG_RESET_ON_FORK flag in attr.sched_flags when calling sched_se‐‐
tattr(2).

Note that the constants used with these two APIs have different names. The state of the re‐
set-on-fork flag can analogously be retrieved using sched_getscheduler(2) and
sched_getattr(2).

The reset-on-fork feature is intended for media-playback applications, and can be used to
prevent applications evading the RLIMIT_RTTIME resource limit (see getrlimit(2)) by creating
multiple child processes.

More precisely, if the reset-on-fork flag is set, the following rules apply for subsequently
created children:

* If the calling thread has a scheduling policy of SCHED_FIFO or SCHED_RR, the policy is re‐
set to SCHED_OTHER in child processes.

* If the calling process has a negative nice value, the nice value is reset to zero in child
processes.

After the reset-on-fork flag has been enabled, it can be reset only if the thread has the
CAP_SYS_NICE capability. This flag is disabled in child processes created by fork(2).

Privileges and resource limits
In Linux kernels before 2.6.12, only privileged (CAP_SYS_NICE) threads can set a nonzero
static priority (i.e., set a real-time scheduling policy). The only change that an unprivi‐
leged thread can make is to set the SCHED_OTHER policy, and this can be done only if the ef‐
fective user ID of the caller matches the real or effective user ID of the target thread
(i.e., the thread specified by pid) whose policy is being changed.

A thread must be privileged (CAP_SYS_NICE) in order to set or modify a SCHED_DEADLINE policy.

Since Linux 2.6.12, the RLIMIT_RTPRIO resource limit defines a ceiling on an unprivileged
thread's static priority for the SCHED_RR and SCHED_FIFO policies. The rules for changing
scheduling policy and priority are as follows:

* If an unprivileged thread has a nonzero RLIMIT_RTPRIO soft limit, then it can change its
scheduling policy and priority, subject to the restriction that the priority cannot be set
to a value higher than the maximum of its current priority and its RLIMIT_RTPRIO soft
limit.

* If the RLIMIT_RTPRIO soft limit is 0, then the only permitted changes are to lower the
priority, or to switch to a non-real-time policy.

* Subject to the same rules, another unprivileged thread can also make these changes, as
long as the effective user ID of the thread making the change matches the real or effec‐
tive user ID of the target thread.

* Special rules apply for the SCHED_IDLE policy. In Linux kernels before 2.6.39, an unpriv‐
ileged thread operating under this policy cannot change its policy, regardless of the
value of its RLIMIT_RTPRIO resource limit. In Linux kernels since 2.6.39, an unprivileged
thread can switch to either the SCHED_BATCH or the SCHED_OTHER policy so long as its nice
value falls within the range permitted by its RLIMIT_NICE resource limit (see getr‐‐
limit(2)).

Privileged (CAP_SYS_NICE) threads ignore the RLIMIT_RTPRIO limit; as with older kernels, they
can make arbitrary changes to scheduling policy and priority. See getrlimit(2) for further
information on RLIMIT_RTPRIO.

Limiting the CPU usage of real-time and deadline processes
A nonblocking infinite loop in a thread scheduled under the SCHED_FIFO, SCHED_RR, or
SCHED_DEADLINE policy can potentially block all other threads from accessing the CPU forever.
Prior to Linux 2.6.25, the only way of preventing a runaway real-time process from freezing
the system was to run (at the console) a shell scheduled under a higher static priority than
the tested application. This allows an emergency kill of tested real-time applications that
do not block or terminate as expected.

Since Linux 2.6.25, there are other techniques for dealing with runaway real-time and dead‐
line processes. One of these is to use the RLIMIT_RTTIME resource limit to set a ceiling on
the CPU time that a real-time process may consume. See getrlimit(2) for details.

Since version 2.6.25, Linux also provides two /proc files that can be used to reserve a cer‐
tain amount of CPU time to be used by non-real-time processes. Reserving CPU time in this
fashion allows some CPU time to be allocated to (say) a root shell that can be used to kill a
runaway process. Both of these files specify time values in microseconds:

/proc/sys/kernel/sched_rt_period_us
This file specifies a scheduling period that is equivalent to 100% CPU bandwidth. The
value in this file can range from 1 to INT_MAX, giving an operating range of 1 mi‐
crosecond to around 35 minutes. The default value in this file is 1,000,000 (1 sec‐
ond).

/proc/sys/kernel/sched_rt_runtime_us
The value in this file specifies how much of the "period" time can be used by all
real-time and deadline scheduled processes on the system. The value in this file can
range from -1 to INT_MAX-1. Specifying -1 makes the run time the same as the period;
that is, no CPU time is set aside for non-real-time processes (which was the Linux be‐
havior before kernel 2.6.25). The default value in this file is 950,000 (0.95 sec‐
onds), meaning that 5% of the CPU time is reserved for processes that don't run under
a real-time or deadline scheduling policy.

Response time
A blocked high priority thread waiting for I/O has a certain response time before it is
scheduled again. The device driver writer can greatly reduce this response time by using a
"slow interrupt" interrupt handler.

Miscellaneous
Child processes inherit the scheduling policy and parameters across a fork(2). The schedul‐
ing policy and parameters are preserved across execve(2).

Memory locking is usually needed for real-time processes to avoid paging delays; this can be
done with mlock(2) or mlockall(2).

The autogroup feature
Since Linux 2.6.38, the kernel provides a feature known as autogrouping to improve interac‐
tive desktop performance in the face of multiprocess, CPU-intensive workloads such as build‐
ing the Linux kernel with large numbers of parallel build processes (i.e., the make(1) -j
flag).

This feature operates in conjunction with the CFS scheduler and requires a kernel that is
configured with CONFIG_SCHED_AUTOGROUP. On a running system, this feature is enabled or dis‐
abled via the file /proc/sys/kernel/sched_autogroup_enabled; a value of 0 disables the fea‐
ture, while a value of 1 enables it. The default value in this file is 1, unless the kernel
was booted with the noautogroup parameter.

A new autogroup is created when a new session is created via setsid(2); this happens, for ex‐
ample, when a new terminal window is started. A new process created by fork(2) inherits its
parent's autogroup membership. Thus, all of the processes in a session are members of the
same autogroup. An autogroup is automatically destroyed when the last process in the group
terminates.

When autogrouping is enabled, all of the members of an autogroup are placed in the same ker‐
nel scheduler "task group". The CFS scheduler employs an algorithm that equalizes the dis‐
tribution of CPU cycles across task groups. The benefits of this for interactive desktop
performance can be described via the following example.

Suppose that there are two autogroups competing for the same CPU (i.e., presume either a sin‐
gle CPU system or the use of taskset(1) to confine all the processes to the same CPU on an
SMP system). The first group contains ten CPU-bound processes from a kernel build started
with make -j10. The other contains a single CPU-bound process: a video player. The effect
of autogrouping is that the two groups will each receive half of the CPU cycles. That is,
the video player will receive 50% of the CPU cycles, rather than just 9% of the cycles, which
would likely lead to degraded video playback. The situation on an SMP system is more com‐
plex, but the general effect is the same: the scheduler distributes CPU cycles across task
groups such that an autogroup that contains a large number of CPU-bound processes does not
end up hogging CPU cycles at the expense of the other jobs on the system.

A process's autogroup (task group) membership can be viewed via the file /proc/[pid]/auto‐
group:

$ cat /proc/1/autogroup
/autogroup-1 nice 0

This file can also be used to modify the CPU bandwidth allocated to an autogroup. This is
done by writing a number in the "nice" range to the file to set the autogroup's nice value.
The allowed range is from +19 (low priority) to -20 (high priority). (Writing values outside
of this range causes write(2) to fail with the error EINVAL.)

The autogroup nice setting has the same meaning as the process nice value, but applies to
distribution of CPU cycles to the autogroup as a whole, based on the relative nice values of
other autogroups. For a process inside an autogroup, the CPU cycles that it receives will be
a product of the autogroup's nice value (compared to other autogroups) and the process's nice
value (compared to other processes in the same autogroup.

The use of the cgroups(7) CPU controller to place processes in cgroups other than the root
CPU cgroup overrides the effect of autogrouping.

The autogroup feature groups only processes scheduled under non-real-time policies
(SCHED_OTHER, SCHED_BATCH, and SCHED_IDLE). It does not group processes scheduled under
real-time and deadline policies. Those processes are scheduled according to the rules de‐
scribed earlier.

The nice value and group scheduling
When scheduling non-real-time processes (i.e., those scheduled under the SCHED_OTHER,
SCHED_BATCH, and SCHED_IDLE policies), the CFS scheduler employs a technique known as "group
scheduling", if the kernel was configured with the CONFIG_FAIR_GROUP_SCHED option (which is
typical).

Under group scheduling, threads are scheduled in "task groups". Task groups have a hierar‐
chical relationship, rooted under the initial task group on the system, known as the "root
task group". Task groups are formed in the following circumstances:

* All of the threads in a CPU cgroup form a task group. The parent of this task group is
the task group of the corresponding parent cgroup.

* If autogrouping is enabled, then all of the threads that are (implicitly) placed in an au‐
togroup (i.e., the same session, as created by setsid(2)) form a task group. Each new au‐
togroup is thus a separate task group. The root task group is the parent of all such au‐
togroups.

* If autogrouping is enabled, then the root task group consists of all processes in the root
CPU cgroup that were not otherwise implicitly placed into a new autogroup.

* If autogrouping is disabled, then the root task group consists of all processes in the
root CPU cgroup.

* If group scheduling was disabled (i.e., the kernel was configured without CON‐‐
FIG_FAIR_GROUP_SCHED), then all of the processes on the system are notionally placed in a
single task group.

Under group scheduling, a thread's nice value has an effect for scheduling decisions only
relative to other threads in the same task group. This has some surprising consequences in
terms of the traditional semantics of the nice value on UNIX systems. In particular, if au‐
togrouping is enabled (which is the default in various distributions), then employing setpri‐‐
ority(2) or nice(1) on a process has an effect only for scheduling relative to other pro‐
cesses executed in the same session (typically: the same terminal window).

Conversely, for two processes that are (for example) the sole CPU-bound processes in differ‐
ent sessions (e.g., different terminal windows, each of whose jobs are tied to different au‐
togroups), modifying the nice value of the process in one of the sessions has no effect in
terms of the scheduler's decisions relative to the process in the other session. A possibly
useful workaround here is to use a command such as the following to modify the autogroup nice
value for all of the processes in a terminal session:

$ echo 10 > /proc/self/autogroup

Real-time features in the mainline Linux kernel
Since kernel version 2.6.18, Linux is gradually becoming equipped with real-time capabili‐
ties, most of which are derived from the former realtime-preempt patch set. Until the
patches have been completely merged into the mainline kernel, they must be installed to
achieve the best real-time performance. These patches are named:

patch-kernelversion-rtpatchversion

and can be downloaded from ⟨http://www.kernel.org/pub/linux/kernel/projects/rt/⟩.

Without the patches and prior to their full inclusion into the mainline kernel, the kernel
configuration offers only the three preemption classes CONFIG_PREEMPT_NONE, CONFIG_PRE‐‐
EMPT_VOLUNTARY, and CONFIG_PREEMPT_DESKTOP which respectively provide no, some, and consider‐
able reduction of the worst-case scheduling latency.

With the patches applied or after their full inclusion into the mainline kernel, the addi‐
tional configuration item CONFIG_PREEMPT_RT becomes available. If this is selected, Linux is
transformed into a regular real-time operating system. The FIFO and RR scheduling policies
are then used to run a thread with true real-time priority and a minimum worst-case schedul‐
ing latency.

NOTES
The cgroups(7) CPU controller can be used to limit the CPU consumption of groups of pro‐
cesses.

Originally, Standard Linux was intended as a general-purpose operating system being able to
handle background processes, interactive applications, and less demanding real-time applica‐
tions (applications that need to usually meet timing deadlines). Although the Linux kernel
2.6 allowed for kernel preemption and the newly introduced O(1) scheduler ensures that the
time needed to schedule is fixed and deterministic irrespective of the number of active
tasks, true real-time computing was not possible up to kernel version 2.6.17.

SEE ALSO
chcpu(1), chrt(1), lscpu(1), ps(1), taskset(1), top(1), getpriority(2), mlock(2),
mlockall(2), munlock(2), munlockall(2), nice(2), sched_get_priority_max(2),
sched_get_priority_min(2), sched_getaffinity(2), sched_getparam(2), sched_getscheduler(2),
sched_rr_get_interval(2), sched_setaffinity(2), sched_setparam(2), sched_setscheduler(2),
sched_yield(2), setpriority(2), pthread_getaffinity_np(3), pthread_getschedparam(3),
pthread_setaffinity_np(3), sched_getcpu(3), capabilities(7), cpuset(7)

Programming for the real world - POSIX.4 by Bill O. Gallmeister, O'Reilly & Associates, Inc.,
ISBN 1-56592-074-0.

The Linux kernel source files Documentation/scheduler/sched-deadline.txt,
Documentation/scheduler/sched-rt-group.txt, Documentation/scheduler/sched-design-CFS.txt, and
Documentation/scheduler/sched-nice-design.txt

COLOPHON
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Linux 2019-08-02 SCHED(7)