affinity(3) - NetBSD Manual Pages

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AFFINITY(3)             NetBSD 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.  Ordi-
     nary 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 8.0                     December 4, 2011                     NetBSD 8.0