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cpuset_getdomain, cpuset_setdomainmanage memory domain policy


Standard C Library (libc, -lc)


#include <sys/param.h>
#include <sys/domainset.h>

cpuset_getdomain(cpulevel_t level, cpuwhich_t which, id_t id, size_t setsize, domainset_t *mask, int *policy);

cpuset_setdomain(cpulevel_t level, cpuwhich_t which, id_t id, size_t setsize, const domainset_t *mask, int policy);


() and cpuset_setdomain() allow the manipulation of sets of memory domains and allocation policy available to processes, threads, jails and other resources. These functions may manipulate sets of memory domains that contain many processes or per-object anonymous masks that affect only a single object.

The valid values for the level and which arguments are documented in cpuset(2). These arguments specify which object and which set of the object we are referring to. Not all possible combinations are valid. For example, only processes may belong to a numbered set accessed by a level argument of CPU_LEVEL_CPUSET. All resources, however, have a mask which may be manipulated with CPU_LEVEL_WHICH.

Masks of type domainset_t are composed using the DOMAINSET macros. The kernel tolerates large sets as long as all domains specified in the set exist. Sets smaller than the kernel uses generate an error on calls to () even if the result set would fit within the user supplied set. Calls to cpuset_setdomain() tolerate small sets with no restrictions.

The supplied mask should have a size of setsize bytes. This size is usually provided by calling sizeof(mask) which is ultimately determined by the value of DOMAINSET_SETSIZE as defined in <sys/domainset.h>.

() retrieves the mask and policy from the object specified by level, which and id and stores it in the space provided by mask and policy.

() attempts to set the mask and policy for the object specified by level, which and id to the values in mask and policy.


Valid policy values are as follows:

Memory is allocated on a round-robin basis by cycling through each domain in mask.
Memory is allocated on the domain local to the CPU the requesting thread is running on. Failure to allocate from this domain will fallback to round-robin.
Memory is allocated preferentially from the single domain specified in the mask. If memory is unavailable the domains listed in the parent cpuset will be visited in a round-robin order.


Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.


The following error codes may be set in errno:

The level or which argument was not a valid value.
The mask or policy argument specified when calling cpuset_setdomain() was not a valid value.
The cpuset_setdomain() call would leave a thread without a valid CPU to run on because the set does not overlap with the thread's anonymous mask.
The mask pointer passed was invalid.
The object specified by the id and which arguments could not be found.
The domainsetsize was either preposterously large or smaller than the kernel set size.
The calling process did not have the credentials required to complete the operation.
The calling process attempted to act on a process other than itself, while in capability mode. See capsicum(4).


capsicum(4), cpuset(1), cpuset(2), cpuset_getid(2), cpuset_setid(2), cpuset_getaffinity(2), cpuset_setaffinity(2), cpuset(9)


The cpuset_getdomain family of system calls first appeared in FreeBSD 12.0.


Jeffrey Roberson <>

June 18, 2020 Debian