DragonFly On-Line Manual Pages

PTHREAD_SETAFFINITY_NP(3)                   DragonFly Library Functions Manual

NAME
     pthread_setaffinity_np, pthread_getaffinity_np - set and get the thread's
     CPU affinity mask

LIBRARY
     POSIX Threads Library (libpthread, -lpthread)

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

     int
     pthread_setaffinity_np(pthread_t tid, size_t cpusetsize,
         const cpu_set_t *mask);

     int
     pthread_getaffinity_np(pthread_t tid, size_t cpusetsize,
         cpu_set_t *mask);

DESCRIPTION
     The pthread_setaffinity_np() sets the CPU affinity mask of the thread
     identified by tid to the value specified by the mask.  The cpusetsize is
     the length (in bytes) of the data pointed to by mask.  Normally this
     argument would be specified as sizeof(cpu_set_t).  If the thread
     specified by the tid is the current thread, it will be migrated
     immediately, if necessary, otherwise it will be migrated by the scheduler
     later.

     A process created by fork(2), vfork(2), and rfork(2) inherits the calling
     thread's CPU affinity mask.  Same applies to the threads created by
     lwp_create(2), and the threads created by pthread_create(3).

     pthread_getaffinity_np() writes the affinity mask of the thread
     identified by the tid to the cpu_set_t structure pointed to by mask.

     The cpu_set_t data structure represents a set of CPUs.  See
     sched_setaffinity(2) for details.

RETURN VALUES
     If successful, these functions will return zero.  Otherwise an error
     number will be returned to indicate the error.

ERRORS
     The pthread_setaffinity_np() and pthread_getaffinity_np() will fail if:

     [EFAULT]           The mask parameter is outside the process's allocated
                        address space.

     [EINVAL]           The tid parameter is invalid.

     [ESRCH]            The thread identified by the tid does not exist.

     [EPERM]            The mask does not contain a valid CPU.

SEE ALSO
     fork(2), lwp_create(2), lwp_getaffinity(2), lwp_setaffinity(2), rfork(2),
     sched_getaffinity(2), sched_setaffinity(2), vfork(2), pthread_create(3)

HISTORY
     The pthread_setaffinity_np() and pthread_getaffinity_np() functions first
     appeared in DragonFly 4.7.

DragonFly 6.3-DEVELOPMENT      January 14, 2017      DragonFly 6.3-DEVELOPMENT