pthread_attr_setaffinity_np(3)                        Library Functions Manual

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 (),             | Thread safety | MT-Safe |
       |pthread_attr_getaffinity_np ()              |               |         |
       +--------------------------------------------+---------------+---------+
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)

Linux man-pages 6.7               2023-10-31    pthread_attr_setaffinity_np(3)