PTHREAD_ATTR_SETAFFINITY_NP(3) Linux Programmer's Manual PTHREAD_ATTR_SETAFFINITY_NP(3)
pthread_attr_setaffinity_np, pthread_attr_getaffinity_np - set/get CPU affinity attribute
in thread attributes object
#define _GNU_SOURCE /* See feature_test_macros(7) */
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
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. Typ-
ically, 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).
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
In glibc 2.3.3 only, versions of these functions were provided that did not have a cpuset-
size argument. Instead the CPU set size given to the underlying system calls was always
sched_setaffinity(2), pthread_attr_init(3), pthread_setaffinity_np(3), cpuset(7),
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Linux 2010-09-10 PTHREAD_ATTR_SETAFFINITY_NP(3)