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AFFINITY(3)                Library Functions Manual                AFFINITY(3)

NAME
     pthread_setaffinity_np, pthread_getaffinity_np - affinity of threads

LIBRARY
     POSIX Threads Library (libpthread, -lpthread)

SYNOPSIS
     #include <pthread.h>
     #include <sched.h>

     int
     pthread_setaffinity_np(pthread_t thread, size_t size, cpuset_t *set);

     int
     pthread_getaffinity_np(pthread_t thread, size_t size, cpuset_t *set);

DESCRIPTION
     Thread affinity allows to run the thread on specified CPU or CPUs only.

     The pthread_setaffinity_np() function sets the affinity mask set for
     thread.  At least one valid CPU must be set in the mask.

     The pthread_getaffinity_np() function gets the affinity mask of thread
     into set.  Note that set must be created and initialized using the
     cpuset(3) functions.

IMPLEMENTATION NOTES
     Setting CPU pthread_setaffinity_np requires super-user privileges.
     Ordinary users can be allowed to control CPU affinity of their threads
     via the security.models.extensions.user_set_cpu_affinity sysctl(7).  See
     secmodel_extensions(9).

     Portable applications should not use the pthread_setaffinity_np() and
     pthread_getaffinity_np() functions.

RETURN VALUES
     The pthread_setaffinity_np() and pthread_getaffinity_np() functions
     return 0 on success.  Otherwise, an error number is returned to indicate
     the error.

EXAMPLES
     An example of code fragment, which sets the affinity for the current
     thread to the CPU whose ID is 0:

             cpuset_t *cset;
             pthread_t pth;
             cpuid_t ci;

             cset = cpuset_create();
             if (cset == NULL) {
                     err(EXIT_FAILURE, "cpuset_create");
             }
             ci = 0;
             cpuset_set(ci, cset);

             pth = pthread_self();
             error = pthread_setaffinity_np(pth, cpuset_size(cset), cset);
             if (error) {
                     ...
             }
             cpuset_destroy(cset);

COMPATIBILITY
     Both functions are non-standard extensions.

ERRORS
     Both functions may fail if:

     [EINVAL]           The specified set was invalid.

     [EPERM]            The calling process lacks the appropriate privileges
                        to perform the operation.

     [ESRCH]            No thread could be found corresponding to the one
                        specified by thread.

NOTES
     There is an alternative processor sets interface, see pset(3).  However,
     thread affinity and processor sets are mutually exclusive, hence mixing
     of these interfaces is prohibited.

SEE ALSO
     cpuset(3), pset(3), pthread_getschedparam(3), pthread_setschedparam(3),
     sched(3), schedctl(8)

NetBSD 10.99                   December 4, 2011                   NetBSD 10.99