Copyright (c) 2008 Jeffrey Roberson
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$FreeBSD: head/lib/libc/sys/cpuset_getaffinity.2 177706 2008-03-29 10:26:29Z jeff $
.Dd March 29, 2008 .Dt CPUSET 2 .Os .Sh NAME .Nm cpuset_getaffinity , .Nm cpuset_setaffinity .Nd manage CPU affinity .Sh LIBRARY .Lb libc .Sh SYNOPSIS n sys/cpuset.h .Ft int .Fn cpuset_getaffinity "cpulevel_t level" "cpuwhich_t which" "id_t id" "size_t setsize" "cpuset_t *mask" .Ft int .Fn cpuset_setaffinity "cpulevel_t level" "cpuwhich_t which" "id_t id" "size_t setsize" "const cpuset_t *mask" .Sh DESCRIPTION .Fn cpuset_getaffinity and .Fn cpuset_setaffinity allow the manipulation of sets of CPUs available to processes, threads, interrupts and other resources. These functions may manipulate sets of CPUs that contain many processes or per-object anonymous masks that effect only a single object.
p The valid values for the .Fa level and .Fa which arguments are documented in .Xr 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 .Fa level argument of .Dv CPU_LEVEL_CPUSET . All resources, however, have a mask which may be manipulated with .Dv CPU_LEVEL_WHICH .
p Masks of type .Ft cpuset_t are composed using the .Xr CPU_SET 2 macros. The kernel tolerates large sets as long as all CPUs specified in the set exist. Sets smaller than the kernel uses generate an error on calls to .Fn cpuset_getaffinity even if the result set would fit within the user supplied set. Calls to .Fn cpuset_setaffinity tolerate small sets with no restrictions.
p The supplied mask should have a size of .Fa setsize bytes. This size is usually provided by calling .Li sizeof(mask) which is ultimately determined by the value of .Dv CPU_SETSIZE as defined in n sys/cpuset.h .
p .Fn cpuset_getaffinity retrieves the mask from the object specified by .Fa level , .Fa which and .Fa id and stores it in the space provided by .Fa mask .
p .Fn cpuset_setaffinity attempts to set the mask for the object specified by .Fa level , .Fa which and .Fa id to the value in .Fa mask .
p .Sh RETURN VALUES .Rv -std .Sh ERRORS The following error codes may be set in .Va errno : l -tag -width Er t Bq Er EINVAL The .Fa level or .Fa which argument was not a valid value. t Bq Er EDEADLK The .Fn cpuset_setaffinity call would leave a thread without a valid CPU to run on because the set does not overlap with the thread's anonymous mask. t Bq Er EFAULT The mask pointer passed was invalid. t Bq Er ESRCH The object specified by the .Fa id and .Fa which arguments could not be found. t Bq Er ERANGE The .Fa cpusetsize was either preposterously large or smaller than the kernel set size. t Bq Er EPERM The calling process did not have the credentials required to complete the operation. .El .Sh SEE ALSO .Xr cpuset 1 , .Xr cpuset 2 , .Xr cpuset_getid 2 , .Xr cpuset_setid 2 , .Xr CPU_SET 3 .Sh HISTORY The .Nm family of system calls first appeared in .Fx 8.0 . .Sh AUTHOR .An Jeffrey Roberson Aq jeff@FreeBSD.org