NAME

       cpuset, cpuset_getid, cpuset_setid — manage CPU affinity sets

LIBRARY

       Standard C Library (libc, -lc)

SYNOPSIS

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

       int
       cpuset(cpusetid_t *setid);

       int
       cpuset_setid(cpuwhich_t which, id_t id, cpusetid_t setid);

       int
       cpuset_getid(cpulevel_t level, cpuwhich_t which, id_t id, cpusetid_t *setid);

DESCRIPTION

       The 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:

             CPU_LEVEL_ROOT      Root set
             CPU_LEVEL_CPUSET    Assigned set
             CPU_LEVEL_WHICH     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:

             CPU_WHICH_TID            id is lwpid_t (thread id)
             CPU_WHICH_PID            id is pid_t (process id)
             CPU_WHICH_JAIL           id is jid (jail id)
             CPU_WHICH_CPUSET         id is a cpusetid_t (cpuset id)
             CPU_WHICH_IRQ            id is an irq number
             CPU_WHICH_INTRHANDLER    id is an irq number for an interrupt handler
             CPU_WHICH_ITHREAD        id is an irq number for an ithread
             CPU_WHICH_DOMAIN         id is a NUMA domain

       An  id  of '-1' may be used with a which of CPU_WHICH_TID, CPU_WHICH_PID, or CPU_WHICH_CPUSET to mean the
       current thread, process, or current thread's cpuset.  All cpuset syscalls allow this usage.

       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
       cpuset_setaffinity(2).

       cpuset() 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 to fork(2).

       cpuset_setid() 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.

       cpuset_getid()  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_CPUSET or 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.

RETURN VALUES

       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.

ERRORS

       The following error codes may be set in errno:

       [EINVAL]           The which or level argument was not a valid value.

       [EDEADLK]          The 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.

       [EFAULT]           The setid pointer passed to cpuset_getid() or cpuset() was invalid.

       [ESRCH]            The object specified by the id and which arguments could not be found.

       [EPERM]            The calling process did not have the credentials required to complete the operation.

       [ENFILE]           There was no free cpusetid_t for allocation.

SEE ALSO

       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)

HISTORY

       The cpuset family of system calls first appeared in FreeBSD 7.1.

AUTHORS

       Jeffrey Roberson <jeff@FreeBSD.org>

Debian                                             May 3, 2017                                         CPUSET(2)