227 lines
6.4 KiB
Groff
227 lines
6.4 KiB
Groff
.\" Copyright (c) 2008 Christian Brueffer
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.\" Copyright (c) 2008 Jeffrey Roberson
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd March 29, 2008
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.Dt CPUSET 2
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.Os
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.Sh NAME
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.Nm cpuset ,
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.Nm cpuset_getid ,
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.Nm cpuset_setid
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.Nd manage CPU affinity sets
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/cpuset.h
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.Ft int
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.Fn cpuset "cpusetid_t *setid"
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.Ft int
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.Fn cpuset_setid "cpuwhich_t which" "id_t id" "cpusetid_t setid"
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.Ft int
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.Fn cpuset_getid "cpulevel_t level" "cpuwhich_t which" "id_t id" "cpusetid_t *setid"
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.Sh DESCRIPTION
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The
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.Nm
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family of system calls allow applications to control sets of processors and
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assign processes and threads to these sets.
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Processor sets contain lists of CPUs that members may run on and exist only
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as long as some process is a member of the set.
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All processes in the system have an assigned set.
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The default set for all processes in the system is the set numbered 1.
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Threads belong to the same set as the process which contains them,
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however, they may further restrict their set with the anonymous
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per-thread mask.
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.Pp
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Sets are referenced by a number of type
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.Ft cpuset_id_t .
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Each thread has a root set, an assigned set, and an anonymous mask.
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Only the root and assigned sets are numbered.
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The root set is the set of all CPUs available in the system or in the
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system partition the thread is running in.
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The assigned set is a subset of the root set and is administratively
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assignable on a per-process basis.
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Many processes and threads may be members of a numbered set.
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.Pp
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The anonymous set is a further thread-specific refinement on the assigned
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set.
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It is intended that administrators will manipulate numbered sets using
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.Xr cpuset 1
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while application developers will manipulate anonymous sets using
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.Xr cpuset_setaffinity 2 .
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.Pp
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To select the correct set a value of type
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.Ft cpulevel_t
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is used.
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The following values for
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.Fa level
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are supported:
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.Bl -column CPU_LEVEL_CPUSET -offset indent
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.It Dv CPU_LEVEL_ROOT Ta "Root set"
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.It Dv CPU_LEVEL_CPUSET Ta "Assigned set"
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.It Dv CPU_LEVEL_WHICH Ta "Set specified by which argument"
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.El
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.Pp
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The
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.Fa which
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argument determines how the value of
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.Fa id
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is interpreted and is of type
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.Ft cpuwhich_t .
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The
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.Fa which
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argument may have the following values:
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.Bl -column CPU_WHICH_CPUSET -offset indent
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.It Dv CPU_WHICH_TID Ta "id is lpwid_t (thread id)"
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.It Dv CPU_WHICH_PID Ta "id is pid_t (process id)"
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.It Dv CPU_WHICH_CPUSET Ta "id is a cpusetid_t (cpuset id)"
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.It Dv CPU_WHICH_IRQ Ta "id is an irq number"
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.El
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.Pp
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An
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.Fa id
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of '-1' may be used with a
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.Fa which
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of
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.Dv CPU_WHICH_TID ,
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.Dv CPU_WHICH_PID ,
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or
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.Dv CPU_WHICH_CPUSET
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to mean the current thread, process, or current thread's
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cpuset.
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All cpuset syscalls allow this usage.
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.Pp
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A
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.Fa level
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argument of
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.Dv CPU_LEVEL_WHICH
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combined with a
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.Fa which
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argument other than
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.Dv CPU_WHICH_CPUSET
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refers to the anonymous mask of the object.
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This mask does not have an id and may only be manipulated with
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.Xr cpuset_setaffinity 2 .
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.Pp
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.Fn cpuset
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creates a new set containing the same CPUs as the root set of the current
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process and stores its id in the space provided by
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.Fa setid .
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On successful completion the calling process joins the set and is the
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only member.
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Children inherit this set after a call to
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.Xr fork 2 .
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.Pp
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.Fn cpuset_setid
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attempts to set the id of the object specified by the
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.Fa which
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argument.
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Currently
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.Dv CPU_WHICH_PID
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is the only acceptable value for which as
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threads do not have an id distinct from their process and the API does
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not permit changing the id of an existing set.
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Upon successful completion all of the threads in the target process will
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be running on CPUs permitted by the set.
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.Pp
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.Fn cpuset_getid
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retrieves a set id from the object indicated by
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.Fa which
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and stores it in the space pointed to by
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.Fa setid .
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The retrieved id may be that of either the root or assigned set
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depending on the value of
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.Fa level .
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.Fa level
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should be
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.Dv CPU_LEVEL_CPUSET
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or
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.Dv CPU_LEVEL_ROOT
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to get the set id from
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the process or thread specified by the
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.Fa id
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argument.
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Specifying
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.Dv CPU_LEVEL_WHICH
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with a process or thread is unsupported since
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this references the unnumbered anonymous mask.
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.Pp
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The actual contents of the sets may be retrieved or manipulated using
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.Xr cpuset_getaffinity 2
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and
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.Xr cpuset_setaffinity 2 .
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See those manual pages for more detail.
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.Sh RETURN VALUES
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.Rv -std
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.Sh ERRORS
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The following error codes may be set in
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.Va errno :
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The
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.Fa which
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or
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.Fa level
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argument was not a valid value.
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.It Bq Er EDEADLK
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The
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.Fn cpuset_setid
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call would leave a thread without a valid CPU to run on because the set
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does not overlap with the thread's anonymous mask.
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.It Bq Er EFAULT
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The setid pointer passed to
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.Fn cpuset_getid
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or
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.Fn cpuset
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was invalid.
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.It Bq Er ESRCH
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The object specified by the
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.Fa id
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and
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.Fa which
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arguments could not be found.
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.It Bq Er EPERM
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The calling process did not have the credentials required to complete the
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operation.
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.It Bq Er ENFILE
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There was no free
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.Fn cpusetid_t
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for allocation.
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.El
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.Sh SEE ALSO
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.Xr cpuset 1 ,
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.Xr cpuset_getaffinity 2 ,
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.Xr cpuset_setaffinity 2 ,
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.Xr CPU_SET 3
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.Sh HISTORY
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The
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.Nm
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family of system calls first appeared in
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.Fx 8.0 .
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.Sh AUTHOR
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.An Jeffrey Roberson Aq jeff@FreeBSD.org
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