DragonFly On-Line Manual Pages

SCHED_SETAFFINITY(2)     DragonFly System Calls Manual    SCHED_SETAFFINITY(2)

NAME
     CPU_AND, CPU_CLR, CPU_COUNT, CPU_EQUAL, CPU_ISSET, CPU_OR, CPU_SET,
     CPU_XOR, CPU_ZERO, sched_setaffinity, sched_getaffinity -- set and get a
     process's CPU affinity mask

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/types.h>
     #include <sys/sched.h>

     int
     sched_setaffinity(pid_t pid, size_t cpusetsize, const cpu_set_t *mask);

     int
     sched_getaffinity(pid_t pid, size_t cpusetsize, cpu_set_t *mask);

     CPU_ZERO(&mask);

     CPU_SET(cpu, &mask);

     CPU_CLR(cpu, &mask);

     CPU_ISSET(cpu, &mask);

     CPU_COUNT(&mask);

     CPU_AND(&dstmask, &srcmask1, &srcmask2);

     CPU_OR(&dstmask, &srcmask1, srcmask2);

     CPU_XOR(&dstmask, &srcmask1, &srcmask2);

     CPU_EQUAL(&mask1, &mask2);

DESCRIPTION
     The sched_setaffinity() sets the CPU affinity mask of the process, which
     is identified by the pid to the value specified by the mask.  The
     cpusetsize is the length (in bytes) of the data pointed to by mask.
     Normally this argument would be specified as sizeof(cpu_set_t).  If the
     pid is zero, then the pid of the calling process is used.  All threads of
     the process identified by pid are affected.  If the calling thread is one
     of the target process's threads, then the calling thread will be migrated
     immediately, if necessary, while other threads of the targt process will
     be migrated by the scheduler later.

     A process created by fork(2), vfork(2), and rfork(2) inherits the calling
     thread's CPU affinity mask.  Same applies to the threads created by
     lwp_create(2), and the threads created by pthread_create(3).

     sched_getaffinity() writes the affinity mask of the process identified by
     the pid to the cpu_set_t structure pointed to by mask.  If the pid is
     zero, then the pid of the calling process is used.  If the process is
     multithreaded, then the CPU affinity mask of the first thread will be
     returned.

     The cpu_set_t data structure represents a set of CPUs.  The first
     available CPU on the system corresponds to a cpu value of 0, the next CPU
     corresponds to a cpu value of 1, and so on and so forth.  The constant
     CPU_SETSIZE specifies a value one greater than the maximum CPU number
     that can be stored in cpu_set_t.  The cpu_set_t should be treated as
     opaque data structure; all manipulation of cpu_set_t should be done via
     the following macros:

     CPU_ZERO()    Reset the mask, so that it contains no CPUs.

     CPU_SET()     Add the cpu to the mask.

     CPU_CLR()     Remove the cpu from the mask.

     CPU_ISSET()   Test to see whether the cpu is a member of the mask.

     CPU_COUNT()   Return the number of CPUs in the mask.

     CPU_AND()     Store the intersection of the srcmask1 and the srcmask2 in
                   the dstmask.  The dstmask could be one of the source masks.

     CPU_OR()      Store the union of the srcmask1 and the srcmask2 in the
                   dstmask.  The dstmask could be one of the source masks.

     CPU_XOR()     Store the XOR of the srcmask1 and the srcmask2 in the
                   dstmask.  The dstmask could be one of the source masks.

     CPU_EQUAL()   Test whether the mask1 and the mask2 contain the same CPUs.

RETURN VALUES
     These system calls return -1 on error and 0 upon successful completion.

ERRORS
     The sched_setaffinity() and sched_getaffinity() will fail if:

     [EFAULT]           The mask parameter is outside the process's allocated
                        address space.

     [EINVAL]           The pid parameter is negative.

     [ESRCH]            The process identified by the pid does not exist.

     [EPERM]            The mask does not contain a valid CPU.

SEE ALSO
     fork(2), lwp_create(2), lwp_getaffinity(2), lwp_setaffinity(2), rfork(2),
     vfork(2), pthread_create(3), pthread_getaffinity_np(3),
     pthread_setaffinity_np(3)

HISTORY
     The sched_setaffinity() and sched_getaffinity() functions first appeared
     in DragonFly 4.7.

DragonFly 4.7                  January 14, 2017                  DragonFly 4.7