NAME

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

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);

       Compile and link with -pthread.

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.

VERSIONS

       These functions are provided by glibc since version 2.3.4.

ATTRIBUTES

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

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

CONFORMING TO

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

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)

COLOPHON

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       information  about  reporting  bugs,  and  the  latest  version  of  this   page,   can   be   found   at
       https://www.kernel.org/doc/man-pages/.