table of contents
|CPUSET(2)||System Calls Manual||CPUSET(2)|
— manage CPU affinity sets
Standard C Library (libc, -lc)
which, id_t id,
which, id_t id,
cpuset family of system calls allow
applications to control sets of processors and memory domains and assign
processes and threads to these sets. Processor sets contain lists of CPUs
and domains that members may run on and exist only as long as some process
is a member of the set. All processes in the system have an assigned set.
The default set for all processes in the system is the set numbered 1.
Threads belong to the same set as the process which contains them, however,
they may further restrict their set with the anonymous per-thread mask to
bind to a specific CPU or subset of CPUs and memory domains.
Sets are referenced by a number of type cpuset_id_t. Each thread has a root set, an assigned set, and an anonymous mask. Only the root and assigned sets are numbered. The root set is the set of all CPUs and memory domains available in the system or in the system partition the thread is running in. The assigned set is a subset of the root set and is administratively assignable on a per-process basis. Many processes and threads may be members of a numbered set.
The anonymous set is a further thread-specific refinement on the assigned set. It is intended that administrators will manipulate numbered sets using cpuset(1) while application developers will manipulate anonymous sets using cpuset_setaffinity(2) and cpuset_setdomain(2).
To select the correct set a value of type cpulevel_t is used. The following values for level are supported:
||Set specified by which argument|
The which argument determines how the value of id is interpreted and is of type cpuwhich_t. The which argument may have the following values:
||id is lwpid_t (thread id)|
||id is pid_t (process id)|
||id is jid (jail id)|
||id is a cpusetid_t (cpuset id)|
||id is an irq number|
||id is an irq number for an interrupt handler|
||id is an irq number for an ithread|
||id is a NUMA domain|
An id of '-1' may be used with a
CPU_WHICH_CPUSET to mean the current thread,
process, or current thread's cpuset. All cpuset syscalls allow this
A level argument of
CPU_LEVEL_WHICH combined with a
which argument other than
CPU_WHICH_CPUSET refers to the anonymous mask of the
object. This mask does not have an id and may only be manipulated with
creates a new set containing the same CPUs as the root set of the current
process and stores its id in the space provided by
setid. On successful completion the calling process
joins the set and is the only member. Children inherit this set after a call
attempts to set the id of the object specified by the
which argument. Currently
CPU_WHICH_PID is the only acceptable value for which
as threads do not have an id distinct from their process and the API does
not permit changing the id of an existing set. Upon successful completion
all of the threads in the target process will be running on CPUs permitted
by the set.
retrieves a set id from the object indicated by which
and stores it in the space pointed to by setid. The
retrieved id may be that of either the root or assigned set depending on the
value of level. level should be
CPU_LEVEL_ROOT to get the set id from the process or
thread specified by the id argument. Specifying
CPU_LEVEL_WHICH with a process or thread is
unsupported since this references the unnumbered anonymous mask.
The actual contents of the sets may be retrieved or manipulated using cpuset_getaffinity(2), cpuset_setaffinity(2), cpuset_getdomain(2), and cpuset_setdomain(2). See those manual pages for more detail.
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 which or level argument was not a valid value.
cpuset_setid() 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 setid pointer passed to
cpuset() was invalid.
- The object specified by the id and which arguments could not be found.
- The calling process did not have the credentials required to complete the operation.
- There was no free cpusetid_t for allocation.
cpuset(1), cpuset_getaffinity(2), cpuset_setaffinity(2), cpuset_getdomain(2), cpuset_setdomain(2), pthread_affinity_np(3), pthread_attr_affinity_np(3), cpuset(9)
cpuset family of system calls first
appeared in FreeBSD 7.1.
Jeffrey Roberson <jeff@FreeBSD.org>
|May 3, 2017||Debian|