mirror of https://github.com/mkerrisk/man-pages
CPU_SET.3: Add description of macros for dynamically allocated CPU sets
Add descriptions of CPU_ALLOC(), CPU_ALLOC_SIZE(), CPU_FREE(), CPU_SET_S(), CPU_CLR_S(), CPU_ISSET_S(), CPU_ZERO_S(), CPU_COUNT_S(), CPU_AND_S(), CPU_OR_S(), CPU_XOR_S(), and CPU_EQUAL_S().
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Michael Kerrisk
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man3/CPU_SET.3
161
man3/CPU_SET.3
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@ -22,10 +22,13 @@
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.TH CPU_SET 2 2008-11-12 "Linux" "Linux Programmer's Manual"
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.TH CPU_SET 2 2008-11-13 "Linux" "Linux Programmer's Manual"
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.SH NAME
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CPU_SET, CPU_CLR, CPU_ISSET, CPU_ZERO, CPU_COUNT,
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CPU_AND, CPU_OR, CPU_XOR, CPU_EQUAL \-
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CPU_AND, CPU_OR, CPU_XOR, CPU_EQUAL,
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CPU_ALLOC, CPU_ALLOC_SIZE, CPU_FREE,
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CPU_SET_S, CPU_CLR_S, CPU_ISSET_S, CPU_ZERO_S,
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CPU_COUNT_S, CPU_AND_S, CPU_OR_S, CPU_XOR_S, CPU_EQUAL_S \-
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macros for manipulating CPU sets
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.SH SYNOPSIS
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.nf
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@ -48,6 +51,28 @@ macros for manipulating CPU sets
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.BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
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.sp
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.BI "int CPU_EQUAL(cpu_set_t *" set1 ", cpu_set_t *" set2 );
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.sp
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.BI "cpu_set_t *CPU_ALLOC(int " num_cpus );
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.BR "void CPU_FREE(cpu_set_t *" set );
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.BI "int CPU_ALLOC_SIZE(int " num_cpus );
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.sp
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.BI "void CPU_ZERO_S(size_t " setsize ", cpu_set_t *" set );
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.sp
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.BI "void CPU_SET_S(int " cpu ", size_t " setsize ", cpu_set_t *" set );
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.BI "void CPU_CLR_S(int " cpu ", size_t " setsize ", cpu_set_t *" set );
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.BI "int CPU_ISSET_S(int " cpu ", size_t " setsize ", cpu_set_t *" set );
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.sp
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.BI "void CPU_COUNT_S(size_t " setsize ", cpu_set_t *" set );
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.sp
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.BI "void CPU_AND_S(size_t " setsize ", cpu_set_t *" destset ,
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.BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
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.BI "void CPU_OR_S(size_t " setsize ", cpu_set_t *" destset ,
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.BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
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.BI "void CPU_XOR_S(size_t " setsize ", cpu_set_t *" destset ,
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.BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
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.sp
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.BI "int CPU_EQUAL_S(size_t " setsize ", cpu_set_t *" set1 \
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", cpu_set_t *" set2 );
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.fi
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.SH DESCRIPTION
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The
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@ -59,7 +84,7 @@ and similar interfaces.
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The following macros are provided to operate on the CPU set
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.IR set :
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.TP 16
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.TP 17
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.BR CPU_ZERO ()
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Clears
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.IR set ,
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@ -100,10 +125,11 @@ value of 1, and so on.
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The constant
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.B CPU_SETSIZE
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(currently 1024) specifies a value one greater than the maximum CPU
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number that can be stored in a CPU set.
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number that can be stored in
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.IR cpu_set_t .
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The following macros perform logical operations on SPU sets:
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.TP 16
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The following macros perform logical operations on CPU sets:
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.TP 17
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.BR CPU_AND ()
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Store the logical AND of the sets
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.I srcset1
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@ -132,25 +158,78 @@ in
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(which may be one of the source sets).
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.TP
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.BR CPU_EQUAL ()
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Tests whether two CPU set contain the same CPUs.
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Test whether two CPU set contain exactly the same CPUs.
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.SS Dynamically sized CPU sets
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Because some applications may require the ability to dynamically
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size CPU sets (e.g., to allocate sets larger than that
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defined by the standard
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.I cpu_set_t
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data type), glibc nowadays provides a set of macros to support this.
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The following macros are used to allocate and deallocate CPU sets:
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.TP 17
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.BR CPU_ALLOC ()
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Allocate a CPU set large enough to hold CPUs
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in the range 0 to
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.IR num_cpus-1 .
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.TP
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.BR CPU_ALLOC_SIZE ()
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Return the size in bytes of the CPU set that would be needed to
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hold CPUs in the range 0 to
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.IR num_cpus-1 .
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.\" FIXME . track this bug
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.\" Currently (glibc 2.8), CPU_ALLOC_SIZE() returns double the
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.\" value that it should. This also causes CPU_ALLOC() to allocate
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.\" twice as much memory as is required.
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.\" http://sourceware.org/bugzilla/show_bug.cgi?id=7029
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.\" Eventually, write this up in BUGS.
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This macro provides the value that can be used for
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.I setsize
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in the
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.BR CPU_*_S ()
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macros described below.
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.TP
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.BR CPU_FREE ()
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Free a CPU set previously allocated by
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.BR CPU_ALLOC ().
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.PP
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The macros whose name ends with "_S" are the analogs of
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the similarly named macros without the suffix.
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These macros perform the same tasks as their analogs,
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but operate on the dynamically allocated CPU set(s) whose size is
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.I setsize
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bytes.
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.SH "RETURN VALUE"
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.BR CPU_ISSET ()
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returns non-zero if
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and
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.BR CPU_ISSET_S ()
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return non-zero if
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.I cpu
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is in
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.IR set ;
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otherwise, it returns 0.
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.BR CPU_COUNT ()
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returns the number of CPUs in
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and
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.BR CPU_COUNT_S ()
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return the number of CPUs in
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.IR set .
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.BR CPU_EQUAL ()
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returns non-zero if the two CPU sets are equal; otherwise it returns 0.
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and
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.BR CPU_EQUAL_S ()
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return non-zero if the two CPU sets are equal; otherwise it returns 0.
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.BR CPU_ALLOC ()
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returns a pointer on success, or NULL on failure.
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(Errors are as for
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.BR malloc (3).)
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.BR CPU_ALLOC_SIZE ()
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returns the number of bytes required to store a
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CPU set of the specified cardinality.
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The other functions do not return a value.
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.\" .SH ERRORS
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.\" AFAICT, no E* errors are occur.
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.SH VERSIONS
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The
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.BR CPU_ZERO (),
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@ -166,14 +245,68 @@ first appeared in glibc 2.6.
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.BR CPU_AND (),
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.BR CPU_OR (),
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.BR CPU_XOR (),
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.BR CPU_EQUAL (),
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.BR CPU_ALLOC (),
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.BR CPU_ALLOC_SIZE (),
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.BR CPU_FREE (),
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.BR CPU_ZERO_S (),
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.BR CPU_SET_S (),
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.BR CPU_CLR_S (),
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.BR CPU_ISSET_S (),
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.BR CPU_AND_S (),
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.BR CPU_OR_S (),
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.BR CPU_XOR_S (),
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and
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.BR CPU_EQUAL ()
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.BR CPU_EQUAL_S ()
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first appeared in glibc 2.7.
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.SH "CONFORMING TO"
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These interfaces are Linux-specific.
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.SH EXAMPLE
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The following program demonstrates the use of some of the macros
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used for dynamically allocated CPU sets.
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.nf
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#define _GNU_SOURCE
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#include <sched.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <assert.h>
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int
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main(int argc, char *argv[])
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{
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cpu_set_t *cpusetp;
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size_t size;
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int num_cpus, cpu;
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if (argc < 2) {
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fprintf(stderr, "Usage: %s <num\-cpus>\\n", argv[0]);
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exit(EXIT_FAILURE);
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}
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num_cpus = atoi(argv[1]);
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cpusetp = CPU_ALLOC(num_cpus);
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if (cpusetp == NULL) {
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perror("CPU_ALLOC");
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exit(EXIT_FAILURE);
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}
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size = CPU_ALLOC_SIZE(num_cpus);
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CPU_ZERO_S(size, cpusetp);
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for (cpu = 0; cpu < num_cpus; cpu += 2)
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CPU_SET_S(cpu, size, cpusetp);
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printf("CPU_COUNT() of set: %d\\n", CPU_COUNT_S(size, cpusetp));
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CPU_FREE(cpusetp);
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exit(EXIT_SUCCESS);
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}
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.fi
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.SH "SEE ALSO"
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.BR sched_setaffinity (2),
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.BR CPU_SET (3),
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.BR pthread_attr_setaffinity_np (3),
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.BR pthread_setaffinity_np (3),
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.BR cpuset (7)
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