PTHREAD_AFFINITY_NP(3)                        FreeBSD Library Functions Manual

NAME
     pthread_getaffinity_np, pthread_setaffinity_np - manage CPU affinity

LIBRARY
     POSIX Threads Library (libpthread, -lpthread)

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),
     pthread_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>.

FreeBSD 13.1-RELEASE-p6        October 12, 2021        FreeBSD 13.1-RELEASE-p6