NAME
pthread_getaffinity_np,
pthread_setaffinity_np —
manage CPU affinity
LIBRARY
library “libpthread”
SYNOPSIS
#include
<pthread_np.h>
int
pthread_getaffinity_np(pthread_t
td, size_t
cpusetsize, cpuset_t
*cpusetp);
int
pthread_setaffinity_np(pthread_t
td, size_t
cpusetsize, const
cpuset_t *cpusetp);
DESCRIPTION
pthread_getaffinity_np()
and pthread_setaffinity_np() allow the manipulation of
sets of CPUs available to the specified thread.
Masks of type
cpuset_t are composed using the
CPU_SET macros. The kernel tolerates large sets as
long as all CPUs specified in the set exist. Sets smaller than the kernel
uses generate an error on calls to
pthread_getaffinity_np()
even if the result set would fit within the user supplied set. Calls to
pthread_setaffinity_np() tolerate small sets with no
restrictions.
The supplied mask should have a size of
cpusetsize bytes. This size is usually provided by
calling sizeof(cpuset_t) which is ultimately
determined by the value of CPU_SETSIZE as defined in
<sys/cpuset.h>.
pthread_getaffinity_np()
retrieves the mask from the thread specified by td,
and stores it in the space provided by cpusetp.
pthread_setaffinity_np()
attempts to set the mask for the thread specified by
td to the value in cpusetp.
RETURN VALUES
If successful, the
pthread_getaffinity_np() and
pthread_setaffinity_np() functions will return zero.
Otherwise an error number will be returned to indicate the error.
ERRORS
The pthread_getaffinity_np() and
pthread_setaffinity_np() functions may fail if:
- [
EDEADLK] - The
pthread_setaffinity_np() call would leave a thread without a valid CPU to run on because the set does not overlap with the thread's anonymous mask. - [
EFAULT] - The cpusetp pointer passed was invalid.
- [
ESRCH] - The thread specified by the td argument could not be found.
- [
ERANGE] - The cpusetsize was either preposterously large or smaller than the kernel set size.
- [
EPERM] - The calling thread did not have the credentials required to complete the operation.
SEE ALSO
cpuset(1), cpuset(2), cpuset_getid(2), cpuset_setid(2), pthread(3), pthread_attr_getaffinity_np(3), pthread_attr_setaffinity_np(3)
STANDARDS
The pthread_getaffinity_np and
pthread_setaffinity_np functions are non-standard
FreeBSD extensions and may be not available on other
operating systems.
HISTORY
The pthread_getaffinity_np and
pthread_setaffinity_np function first appeared in
FreeBSD 7.2.
AUTHORS
The pthread_getaffinity_np and
pthread_setaffinity_np functions were written by
David Xu
<davidxu@FreeBSD.org>,
and this manpage was written by Xin LI
<delphij@FreeBSD.org>.