NAME
pthread_attr_getaffinity_np, pthread_attr_setaffinity_np – manage CPU affinity in thread attribute objects
LIBRARY
POSIX Threads Library (libpthread, -lpthread)
SYNOPSIS
#include <pthread_np.h>
int
pthread_attr_getaffinity_np(const pthread_attr_t *pattr, size_t cpusetsize, cpuset_t *cpusetp);
int
pthread_attr_setaffinity_np(pthread_attr_t *pattr, size_t cpusetsize, const cpuset_t *cpusetp);
DESCRIPTION
The pthread_attr_getaffinity_np() and pthread_attr_setaffinity_np() functions allow the manipulation of sets of CPUs available to the specified thread attribute object.
Masks of type cpuset_t are composed using the CPU_SET macros. If the user-supplied mask is not large enough to fit all of the matching CPUs, pthread_attr_getaffinity_np() fails with ERANGE. Calls to pthread_attr_setaffinity_np() tolerate masks of any size with no restrictions. pthread_attr_setaffinity_np() uses the meaningful part of the mask, where the upper bound is the maximum CPU id present in the system. If bits for non-existing CPUs are set, calls to pthread_attr_setaffinity_np() fail with EINVAL.
The supplied mask should have a size of cpusetsize bytes. This size is usually provided by calling sizeof(cpuset_t) which is ultimately determined by the value of CPU_SETSIZE as defined in ⟨sys/cpuset.h⟩.
pthread_attr_getaffinity_np() retrieves the mask from the thread attribute object specified by pattr, and stores it in the space provided by cpusetp.
pthread_attr_setaffinity_np() sets the mask for the thread attribute object specified by pattr to the value in cpusetp.
RETURN VALUES
If successful, the pthread_attr_getaffinity_np() and pthread_attr_setaffinity_np() functions will return zero. Otherwise an error number will be returned to indicate the error.
ERRORS
The pthread_attr_getaffinity_np() functions will fail if:
- [EINVAL]
-
The pattr or the attribute specified by it is NULL.
- [ERANGE]
-
The cpusetsize is too small.
The pthread_attr_setaffinity_np() function will fail if:
- [EINVAL]
-
The pattr or the attribute specified by it is NULL.
- [EINVAL]
-
The cpusetp specified a CPU that was outside the set supported by the kernel.
- [ENOMEM]
-
Insufficient memory exists to store the cpuset mask.
SEE ALSO
cpuset(1), cpuset(2), cpuset_getid(2), cpuset_setid(2), pthread_getaffinity_np(3), pthread_np(3), pthread_setaffinity_np(3)
STANDARDS
The pthread_attr_getaffinity_np and pthread_attr_setaffinity_np functions are non-standard FreeBSD extensions and may be not available on other operating systems.
HISTORY
The pthread_attr_getaffinity_np and pthread_attr_setaffinity_np functions first appeared in FreeBSD 7.2.
AUTHORS
The pthread_attr_getaffinity_np and pthread_attr_setaffinity_np functions were written by David Xu ⟨[email protected]⟩, and this manpage was written by Xin LI ⟨[email protected]⟩.