62801712df
Since f35093f8 semantics of a thread affinity functions is changed to be a compatible with Linux: In case of getaffinity(), the minimum cpuset_t size that the kernel permits is the maximum CPU id, present in the system, / NBBY bytes, the maximum size is not limited. In case of setaffinity(), the kernel does not limit the size of the user-provided cpuset_t, internally using only the meaningful part of the set, where the upper bound is the maximum CPU id, present in the system, no larger than the size of the kernel cpuset_t. Reviewed by: jhb, kib Differential Revision: https://reviews.freebsd.org/D38111 MFC after: 1 week
165 lines
4.4 KiB
Groff
165 lines
4.4 KiB
Groff
.\"-
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.\" Copyright (c) 2010 Xin LI <delphij@FreeBSD.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 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 January 29, 2023
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.Dt PTHREAD_AFFINITY_NP 3
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.Os
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.Sh NAME
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.Nm pthread_getaffinity_np ,
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.Nm pthread_setaffinity_np
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.Nd manage CPU affinity
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.Sh LIBRARY
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.Lb libpthread
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.Sh SYNOPSIS
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.In pthread_np.h
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.Ft int
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.Fn pthread_getaffinity_np "pthread_t td" "size_t cpusetsize" "cpuset_t *cpusetp"
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.Ft int
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.Fn pthread_setaffinity_np "pthread_t td" "size_t cpusetsize" "const cpuset_t *cpusetp"
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.Sh DESCRIPTION
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.Fn pthread_getaffinity_np
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and
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.Fn pthread_setaffinity_np
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allow the manipulation of sets of CPUs available to the specified thread.
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.Pp
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Masks of type
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.Ft cpuset_t
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are composed using the
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.Dv CPU_SET
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macros.
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If the user-supplied mask is not large enough to fit all of the matching CPUs,
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.Fn pthread_getaffinity_np
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fails with
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.Er ERANGE .
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Calls to
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.Fn pthread_setaffinity_np
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tolerate masks of any size with no restrictions.
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The kernel uses the meaningful part of the mask, where the upper bound is
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the maximum CPU id present in the system.
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If bits for non-existing CPUs are set, calls to
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.Fn pthread_setaffinity_np
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fails with
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.Er EINVAL .
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.Pp
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The supplied mask should have a size of
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.Fa cpusetsize
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bytes.
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This size is usually provided by calling
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.Li sizeof(cpuset_t)
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which is ultimately determined by the value of
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.Dv CPU_SETSIZE
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as defined in
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.In sys/cpuset.h .
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.Pp
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.Fn pthread_getaffinity_np
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retrieves the
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mask from the thread specified by
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.Fa td ,
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and stores it in the space provided by
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.Fa cpusetp .
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.Pp
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.Fn pthread_setaffinity_np
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attempts to set the mask for the thread specified by
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.Fa td
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to the value in
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.Fa cpusetp .
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.Sh RETURN VALUES
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If successful, the
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.Fn pthread_getaffinity_np
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and
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.Fn pthread_setaffinity_np
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functions will return zero.
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Otherwise an error number will be returned
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to indicate the error.
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.Sh ERRORS
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The
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.Fn pthread_getaffinity_np
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and
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.Fn pthread_setaffinity_np
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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
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.Fa cpusetp
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argument specified when calling
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.Fn pthread_setaffinity_np
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was not a valid value.
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.It Bq Er EDEADLK
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The
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.Fn pthread_setaffinity_np
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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
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.Fa cpusetp
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pointer passed was invalid.
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.It Bq Er ESRCH
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The thread specified by the
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.Fa td
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argument could not be found.
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.It Bq Er ERANGE
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The
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.Fa cpusetsize
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was smaller than needed to fit all of the matching CPUs.
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.It Bq Er EPERM
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The calling thread did not have the credentials required to complete the
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operation.
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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 2 ,
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.Xr cpuset_getid 2 ,
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.Xr cpuset_setid 2 ,
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.Xr pthread 3 ,
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.Xr pthread_attr_getaffinity_np 3 ,
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.Xr pthread_attr_setaffinity_np 3 ,
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.Xr pthread_np 3
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.Sh STANDARDS
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The
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.Nm pthread_getaffinity_np
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and
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.Nm pthread_setaffinity_np
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functions are non-standard
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.Fx
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extensions and may be not available on other operating systems.
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.Sh HISTORY
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The
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.Nm pthread_getaffinity_np
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and
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.Nm pthread_setaffinity_np
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function first appeared in
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.Fx 7.2 .
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm pthread_getaffinity_np
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and
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.Nm pthread_setaffinity_np
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functions were written by
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.An David Xu Aq Mt davidxu@FreeBSD.org ,
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and this manpage was written by
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.An Xin LI Aq Mt delphij@FreeBSD.org .
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