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    Command:

    pthread_getaffinity_np

    
    
    
    

    SYNOPSIS

           #define _GNU_SOURCE             /* See feature_test_macros(7) */
           #include <pthread.h>
    
           int pthread_setaffinity_np(pthread_t thread, size_t cpusetsize,
                                      const cpu_set_t *cpuset);
           int pthread_getaffinity_np(pthread_t thread, size_t cpusetsize,
                                      cpu_set_t *cpuset);
    
           Compile and link with -pthread.
    
    
    

    DESCRIPTION

           The pthread_setaffinity_np() function sets the CPU affinity mask of the
           thread thread to the CPU set pointed to by cpuset.  If the call is suc-
           cessful, and the thread is not currently running on one of the CPUs  in
           cpuset, then it is migrated to one of those CPUs.
    
           The  pthread_getaffinity_np() function returns the CPU affinity mask of
           the thread thread in the buffer pointed to by cpuset.
    
           For more details on CPU affinity masks, see sched_setaffinity(2).   For
           a  description  of  a  set of macros that can be used to manipulate and
           inspect CPU sets, see CPU_SET(3).
    
           The argument cpusetsize is the length (in bytes) of the buffer  pointed
           to   by  cpuset.   Typically,  this  argument  would  be  specified  as
           sizeof(cpu_set_t).  (It may be some other value, if  using  the  macros
           described in CPU_SET(3) for dynamically allocating a CPU set.)
    
    
    

    RETURN VALUE

           On  success,  these functions return 0; on error, they return a nonzero
           error number.
    
    
    

    ERRORS

           EFAULT A supplied memory address was invalid.
    
           EINVAL (pthread_setaffinity_np()) The affinity bit mask  mask  contains
                  no  processors  that  are currently physically on the system and
                  permitted to the thread according to any restrictions  that  may
                  be imposed by the "cpuset" mechanism described in cpuset(7).
    
           EINVAL (pthread_setaffinity_np())  cpuset specified a CPU that was out-
                  side the set supported by the kernel.  (The kernel configuration
                  option  CONFIG_NR_CPUS defines the range of the set supported by
                  the kernel data type used to represent CPU sets.)
    
           EINVAL (pthread_getaffinity_np()) cpusetsize is smaller than  the  size
                  of the affinity mask used by the kernel.
    
           ESRCH  No thread with the ID thread could be found.
    
           run are silently imposed by the kernel.
    
           These functions are implemented on top of the sched_setaffinity(2)  and
           sched_getaffinity(2) system calls.
    
           In glibc 2.3.3 only, versions of these functions were provided that did
           not have a cpusetsize argument.  Instead the CPU set size given to  the
           underlying system calls was always sizeof(cpu_set_t).
    
           A  new  thread created by pthread_create(3) inherits a copy of its cre-
           ator's CPU affinity mask.
    
    
    

    EXAMPLE

           In the following program, the main thread uses pthread_setaffinity_np()
           to  set its CPU affinity mask to include CPUs 0 to 7 (which may not all
           be available on the system), and then calls pthread_getaffinity_np() to
           check the resulting CPU affinity mask of the thread.
    
           #define _GNU_SOURCE
           #include <pthread.h>
           #include <stdio.h>
           #include <stdlib.h>
           #include <errno.h>
    
           #define handle_error_en(en, msg) \
                   do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
    
           int
           main(int argc, char *argv[])
           {
               int s, j;
               cpu_set_t cpuset;
               pthread_t thread;
    
               thread = pthread_self();
    
               /* Set affinity mask to include CPUs 0 to 7 */
    
               CPU_ZERO(&cpuset);
               for (j = 0; j < 8; j++)
                   CPU_SET(j, &cpuset);
    
               s = pthread_setaffinity_np(thread, sizeof(cpu_set_t), &cpuset);
               if (s != 0)
                   handle_error_en(s, "pthread_setaffinity_np");
    
               /* Check the actual affinity mask assigned to the thread */
    
               s = pthread_getaffinity_np(thread, sizeof(cpu_set_t), &cpuset);
               if (s != 0)
                   handle_error_en(s, "pthread_getaffinity_np");
    
    
    

    Linux 2010-09-10 PTHREAD_SETAFFINITY_NP(3)

    
    
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