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       pthread_attr_setaffinity_np,  pthread_attr_getaffinity_np - set/get CPU
       affinity attribute in thread attributes object


       #define _GNU_SOURCE
       #include <pthread.h>

       int pthread_attr_setaffinity_np(pthread_attr_t *attr,
                          size_t cpusetsize, const cpu_set_t *cpuset);
       int pthread_attr_getaffinity_np(pthread_attr_t *attr,
                          size_t cpusetsize, cpu_set_t *cpuset);

       Compile and link with -pthread.


       The pthread_attr_setaffinity_np() function sets the CPU  affinity  mask
       attribute  of  the  thread attributes object referred to by attr to the
       value specified in cpuset.  This attribute determines the CPU  affinity
       mask of a thread created using the thread attributes object attr.

       The  pthread_attr_getaffinity_np()  function  returns  the CPU affinity
       mask attribute of the thread attributes object referred to by  attr  in
       the buffer pointed to by cpuset.

       The  argument cpusetsize is the length (in bytes) of the buffer pointed
       to  by  cpuset.   Typically,  this  argument  would  be  specified   as

       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).


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


       EINVAL (pthread_attr_setaffinity_np()) cpuset specified a CPU that  was
              outside   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_attr_getaffinity_np())  A  CPU  in the affinity mask of
              the thread attributes object referred to by  attr  lies  outside
              the  range  specified  by cpusetsize (i.e., cpuset/cpusetsize is
              too small).

       ENOMEM (pthread_attr_setaffinity_np()) Could not allocate memory.


       These functions are provided by glibc since version 2.3.4.


       These functions are nonstandard GNU extensions; hence the suffix  "_np"
       (nonportable) in the names.


       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).


       sched_setaffinity(2),  pthread_attr_init(3), pthread_setaffinity_np(3),
       cpuset(7), pthreads(7)


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