1 .\" Copyright (C) 2006 Michael Kerrisk
2 .\" and Copyright (C) 2008 Linux Foundation, written by Michael Kerrisk
3 .\" <mtk.manpages@gmail.com>
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27 .TH CPU_SET 3 2012-03-15 "Linux" "Linux Programmer's Manual"
29 CPU_SET, CPU_CLR, CPU_ISSET, CPU_ZERO, CPU_COUNT,
30 CPU_AND, CPU_OR, CPU_XOR, CPU_EQUAL,
31 CPU_ALLOC, CPU_ALLOC_SIZE, CPU_FREE,
32 CPU_SET_S, CPU_CLR_S, CPU_ISSET_S, CPU_ZERO_S,
33 CPU_COUNT_S, CPU_AND_S, CPU_OR_S, CPU_XOR_S, CPU_EQUAL_S \-
34 macros for manipulating CPU sets
37 .BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */"
40 .BI "void CPU_ZERO(cpu_set_t *" set );
42 .BI "void CPU_SET(int " cpu ", cpu_set_t *" set );
43 .BI "void CPU_CLR(int " cpu ", cpu_set_t *" set );
44 .BI "int CPU_ISSET(int " cpu ", cpu_set_t *" set );
46 .BI "int CPU_COUNT(cpu_set_t *" set );
48 .BI "void CPU_AND(cpu_set_t *" destset ,
49 .BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
50 .BI "void CPU_OR(cpu_set_t *" destset ,
51 .BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
52 .BI "void CPU_XOR(cpu_set_t *" destset ,
53 .BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
55 .BI "int CPU_EQUAL(cpu_set_t *" set1 ", cpu_set_t *" set2 );
57 .BI "cpu_set_t *CPU_ALLOC(int " num_cpus );
58 .BI "void CPU_FREE(cpu_set_t *" set );
59 .BI "size_t CPU_ALLOC_SIZE(int " num_cpus );
61 .BI "void CPU_ZERO_S(size_t " setsize ", cpu_set_t *" set );
63 .BI "void CPU_SET_S(int " cpu ", size_t " setsize ", cpu_set_t *" set );
64 .BI "void CPU_CLR_S(int " cpu ", size_t " setsize ", cpu_set_t *" set );
65 .BI "int CPU_ISSET_S(int " cpu ", size_t " setsize ", cpu_set_t *" set );
67 .BI "int CPU_COUNT_S(size_t " setsize ", cpu_set_t *" set );
69 .BI "void CPU_AND_S(size_t " setsize ", cpu_set_t *" destset ,
70 .BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
71 .BI "void CPU_OR_S(size_t " setsize ", cpu_set_t *" destset ,
72 .BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
73 .BI "void CPU_XOR_S(size_t " setsize ", cpu_set_t *" destset ,
74 .BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
76 .BI "int CPU_EQUAL_S(size_t " setsize ", cpu_set_t *" set1 \
77 ", cpu_set_t *" set2 );
82 data structure represents a set of CPUs.
84 .BR sched_setaffinity (2)
85 and similar interfaces.
89 data type is implemented as a bitset.
90 However, the data structure treated as considered opaque:
91 all manipulation of CPU sets should be done via the macros
92 described in this page.
94 The following macros are provided to operate on the CPU set
100 so that it contains no CPUs.
121 Return the number of CPUs in
126 argument is specified, it should not produce side effects,
127 since the above macros may evaluate the argument more than once.
129 The first available CPU on the system corresponds to a
131 value of 0, the next CPU corresponds to a
133 value of 1, and so on.
136 (currently 1024) specifies a value one greater than the maximum CPU
137 number that can be stored in
140 The following macros perform logical operations on CPU sets:
143 Store the intersection of the sets
149 (which may be one of the source sets).
152 Store the union of the sets
158 (which may be one of the source sets).
161 Store the XOR of the sets
167 (which may be one of the source sets).
168 The XOR means the set of CPUs that are in either
175 Test whether two CPU set contain exactly the same CPUs.
176 .SS Dynamically sized CPU sets
177 Because some applications may require the ability to dynamically
178 size CPU sets (e.g., to allocate sets larger than that
179 defined by the standard
181 data type), glibc nowadays provides a set of macros to support this.
183 The following macros are used to allocate and deallocate CPU sets:
186 Allocate a CPU set large enough to hold CPUs
190 .BR CPU_ALLOC_SIZE ()
191 Return the size in bytes of the CPU set that would be needed to
192 hold CPUs in the range 0 to
194 This macro provides the value that can be used for the
198 macros described below.
201 Free a CPU set previously allocated by
204 The macros whose names end with "_S" are the analogs of
205 the similarly named macros without the suffix.
206 These macros perform the same tasks as their analogs,
207 but operate on the dynamically allocated CPU set(s) whose size is
218 otherwise, it returns 0.
223 return the number of CPUs in
229 return nonzero if the two CPU sets are equal; otherwise it returns 0.
232 returns a pointer on success, or NULL on failure.
236 .BR CPU_ALLOC_SIZE ()
237 returns the number of bytes required to store a
238 CPU set of the specified cardinality.
240 The other functions do not return a value.
248 macros were added in glibc 2.3.3.
251 first appeared in glibc 2.6.
258 .BR CPU_ALLOC_SIZE (),
269 first appeared in glibc 2.7.
271 These interfaces are Linux-specific.
273 To duplicate a CPU set, use
276 Since CPU sets are bitsets allocated in units of long words,
277 the actual number of CPUs in a dynamically
278 allocated CPU set will be rounded up to the next multiple of
279 .IR "sizeof(unsigned long)" .
280 An application should consider the contents of these extra bits
283 Notwithstanding the similarity in the names,
284 note that the constant
286 indicates the number of CPUs in the
288 data type (thus, it is effectively a count of bits in the bitset),
293 macros is a size in bytes.
295 The data types for arguments and return values shown
296 in the SYNOPSIS are hints what about is expected in each case.
297 However, since these interfaces are implemented as macros,
298 the compiler won't necessarily catch all type errors
299 if you violate the suggestions.
301 On 32-bit platforms with glibc 2.8 and earlier,
303 allocates twice as much space as is required, and
304 .BR CPU_ALLOC_SIZE ()
305 returns a value twice as large as it should.
306 This bug should not affect the semantics of a program,
307 but does result in wasted memory
308 and less efficient operation of the macros that
309 operate on dynamically allocated CPU sets.
310 These bugs are fixed in glibc 2.9.
311 .\" http://sourceware.org/bugzilla/show_bug.cgi?id=7029
313 The following program demonstrates the use of some of the macros
314 used for dynamically allocated CPU sets.
325 main(int argc, char *argv[])
332 fprintf(stderr, "Usage: %s <num\-cpus>\\n", argv[0]);
336 num_cpus = atoi(argv[1]);
338 cpusetp = CPU_ALLOC(num_cpus);
339 if (cpusetp == NULL) {
344 size = CPU_ALLOC_SIZE(num_cpus);
346 CPU_ZERO_S(size, cpusetp);
347 for (cpu = 0; cpu < num_cpus; cpu += 2)
348 CPU_SET_S(cpu, size, cpusetp);
350 printf("CPU_COUNT() of set: %d\\n", CPU_COUNT_S(size, cpusetp));
357 .BR sched_setaffinity (2),
358 .BR pthread_attr_setaffinity_np (3),
359 .BR pthread_setaffinity_np (3),
362 This page is part of release 3.65 of the Linux
365 A description of the project,
366 and information about reporting bugs,
368 \%http://www.kernel.org/doc/man\-pages/.