141 lines
3.9 KiB
Groff
141 lines
3.9 KiB
Groff
.\" $NetBSD: affinity.3,v 1.8 2011/12/05 10:27:40 wiz Exp $
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.\"
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.\" Copyright (c) 2008 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Mindaugas Rasiukevicius <rmind at NetBSD org>.
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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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd December 4, 2011
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.Dt AFFINITY 3
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.Os
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.Sh NAME
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.Nm pthread_setaffinity_np ,
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.Nm pthread_getaffinity_np
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.Nd affinity of threads
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.Sh LIBRARY
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.Lb libpthread
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.Sh SYNOPSIS
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.In pthread.h
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.In sched.h
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.Ft int
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.Fn pthread_setaffinity_np "pthread_t thread" "size_t size" "cpuset_t *set"
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.Ft int
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.Fn pthread_getaffinity_np "pthread_t thread" "size_t size" "cpuset_t *set"
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.Sh DESCRIPTION
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Thread affinity allows to run the thread on specified CPU or CPUs only.
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.Pp
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The
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.Fn pthread_setaffinity_np
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function sets the affinity mask
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.Fa set
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for
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.Fa thread .
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At least one valid CPU must be set in the mask.
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.Pp
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The
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.Fn pthread_getaffinity_np
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function gets the affinity mask of
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.Fa thread
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into
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.Fa set .
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Note that
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.Fa set
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must be created and initialized using the
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.Xr cpuset 3
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functions.
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.Sh IMPLEMENTATION NOTES
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Setting CPU
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.Nm
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requires super-user privileges.
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Ordinary users can be allowed to control CPU affinity
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of their threads via the
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.Pa security.models.extensions.user_set_cpu_affinity
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.Xr sysctl 7 .
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See
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.Xr secmodel_extensions 9 .
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.Pp
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Portable applications should not use the
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.Fn pthread_setaffinity_np
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and
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.Fn pthread_getaffinity_np
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functions.
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.Sh RETURN VALUES
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The
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.Fn pthread_setaffinity_np
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and
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.Fn pthread_getaffinity_np
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functions return 0 on success.
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Otherwise, an error number is returned to indicate the error.
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.Sh EXAMPLES
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An example of code fragment, which sets the affinity for the current
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thread to the CPU whose ID is 0:
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.Bd -literal
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cpuset_t *cset;
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pthread_t pth;
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cpuid_t ci;
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cset = cpuset_create();
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if (cset == NULL) {
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err(EXIT_FAILURE, "cpuset_create");
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}
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ci = 0;
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cpuset_set(ci, cset);
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pth = pthread_self();
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error = pthread_setaffinity_np(pth, cpuset_size(cset), cset);
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if (error) {
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...
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}
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cpuset_destroy(cset);
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.Ed
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.Sh COMPATIBILITY
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Both functions are non-standard extensions.
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.Sh ERRORS
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Both functions may fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The specified
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.Fa set
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was invalid.
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.It Bq Er EPERM
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The calling process lacks the appropriate privileges to perform
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the operation.
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.It Bq Er ESRCH
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No thread could be found corresponding to the one specified by
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.Fa thread .
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.El
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.Sh NOTES
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There is an alternative processor sets interface, see
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.Xr pset 3 .
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However, thread affinity and processor sets are mutually exclusive,
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hence mixing of these interfaces is prohibited.
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.Sh SEE ALSO
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.Xr cpuset 3 ,
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.Xr pset 3 ,
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.Xr pthread_getschedparam 3 ,
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.Xr pthread_setschedparam 3 ,
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.Xr sched 3 ,
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.Xr schedctl 8
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