NAME

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

LIBRARY

       POSIX threads library (libpthread, -lpthread)

SYNOPSIS

       #define _GNU_SOURCE             /* See feature_test_macros(7) */
       #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(const pthread_attr_t *attr,
                          size_t cpusetsize, cpu_set_t *cpuset);

DESCRIPTION

       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 sizeof(cpu_set_t).

       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).

RETURN VALUE

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

ERRORS

       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.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                                                     │ Attribute     │ Value   │
       ├──────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │pthread_attr_setaffinity_np(), pthread_attr_getaffinity_np()                  │ Thread safety │ MT-Safe │
       └──────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       GNU; hence the suffix "_np" (nonportable) in the names.

HISTORY

       glibc 2.3.4.

NOTES

       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).

SEE ALSO

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