oracular (2) cpuset.2freebsd.gz

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>