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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25 .TH CPU_SET 3 2010-02-21 "Linux" "Linux Programmer's Manual"
27 CPU_SET, CPU_CLR, CPU_ISSET, CPU_ZERO, CPU_COUNT,
28 CPU_AND, CPU_OR, CPU_XOR, CPU_EQUAL,
29 CPU_ALLOC, CPU_ALLOC_SIZE, CPU_FREE,
30 CPU_SET_S, CPU_CLR_S, CPU_ISSET_S, CPU_ZERO_S,
31 CPU_COUNT_S, CPU_AND_S, CPU_OR_S, CPU_XOR_S, CPU_EQUAL_S \-
32 macros for manipulating CPU sets
35 .B #define _GNU_SOURCE
38 .BI "void CPU_ZERO(cpu_set_t *" set );
40 .BI "void CPU_SET(int " cpu ", cpu_set_t *" set );
41 .BI "void CPU_CLR(int " cpu ", cpu_set_t *" set );
42 .BI "int CPU_ISSET(int " cpu ", cpu_set_t *" set );
44 .BI "int CPU_COUNT(cpu_set_t *" set );
46 .BI "void CPU_AND(cpu_set_t *" destset ,
47 .BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
48 .BI "void CPU_OR(cpu_set_t *" destset ,
49 .BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
50 .BI "void CPU_XOR(cpu_set_t *" destset ,
51 .BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
53 .BI "int CPU_EQUAL(cpu_set_t *" set1 ", cpu_set_t *" set2 );
55 .BI "cpu_set_t *CPU_ALLOC(int " num_cpus );
56 .BI "void CPU_FREE(cpu_set_t *" set );
57 .BI "size_t CPU_ALLOC_SIZE(int " num_cpus );
59 .BI "void CPU_ZERO_S(size_t " setsize ", cpu_set_t *" set );
61 .BI "void CPU_SET_S(int " cpu ", size_t " setsize ", cpu_set_t *" set );
62 .BI "void CPU_CLR_S(int " cpu ", size_t " setsize ", cpu_set_t *" set );
63 .BI "int CPU_ISSET_S(int " cpu ", size_t " setsize ", cpu_set_t *" set );
65 .BI "int CPU_COUNT_S(size_t " setsize ", cpu_set_t *" set );
67 .BI "void CPU_AND_S(size_t " setsize ", cpu_set_t *" destset ,
68 .BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
69 .BI "void CPU_OR_S(size_t " setsize ", cpu_set_t *" destset ,
70 .BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
71 .BI "void CPU_XOR_S(size_t " setsize ", cpu_set_t *" destset ,
72 .BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 );
74 .BI "int CPU_EQUAL_S(size_t " setsize ", cpu_set_t *" set1 \
75 ", cpu_set_t *" set2 );
80 data structure represents a set of CPUs.
82 .BR sched_setaffinity (2)
83 and similar interfaces.
87 data type is implemented as a bitset.
88 However, the data structure treated as considered opaque:
89 all manipulation of CPU sets should be done via the macros
90 described in this page.
92 The following macros are provided to operate on the CPU set
98 so that it contains no CPUs.
119 Return the number of CPUs in
124 argument is specified, it should not produce side effects,
125 since the above macros may evaluate the argument more than once.
127 The first available CPU on the system corresponds to a
129 value of 0, the next CPU corresponds to a
131 value of 1, and so on.
134 (currently 1024) specifies a value one greater than the maximum CPU
135 number that can be stored in
138 The following macros perform logical operations on CPU sets:
141 Store the logical AND of the sets
147 (which may be one of the source sets).
150 Store the logical OR of the sets
156 (which may be one of the source sets).
159 Store the logical XOR of the sets
165 (which may be one of the source sets).
168 Test whether two CPU set contain exactly the same CPUs.
169 .SS Dynamically sized CPU sets
170 Because some applications may require the ability to dynamically
171 size CPU sets (e.g., to allocate sets larger than that
172 defined by the standard
174 data type), glibc nowadays provides a set of macros to support this.
176 The following macros are used to allocate and deallocate CPU sets:
179 Allocate a CPU set large enough to hold CPUs
183 .BR CPU_ALLOC_SIZE ()
184 Return the size in bytes of the CPU set that would be needed to
185 hold CPUs in the range 0 to
187 This macro provides the value that can be used for the
191 macros described below.
194 Free a CPU set previously allocated by
197 The macros whose names end with "_S" are the analogs of
198 the similarly named macros without the suffix.
199 These macros perform the same tasks as their analogs,
200 but operate on the dynamically allocated CPU set(s) whose size is
211 otherwise, it returns 0.
216 return the number of CPUs in
222 return nonzero if the two CPU sets are equal; otherwise it returns 0.
225 returns a pointer on success, or NULL on failure.
229 .BR CPU_ALLOC_SIZE ()
230 returns the number of bytes required to store a
231 CPU set of the specified cardinality.
233 The other functions do not return a value.
241 macros were added in glibc 2.3.3.
244 first appeared in glibc 2.6.
251 .BR CPU_ALLOC_SIZE (),
262 first appeared in glibc 2.7.
264 These interfaces are Linux-specific.
266 To duplicate a CPU set, use
269 Since CPU sets are bitsets allocated in units of long words,
270 the actual number of CPUs in a dynamically
271 allocated CPU set will be rounded up to the next multiple of
272 .IR "sizeof(unsigned long)" .
273 An application should consider the contents of these extra bits
276 Notwithstanding the similarity in the names,
277 note that the constant
279 indicates the number of CPUs in the
281 data type (thus, it is effectively a count of bits in the bitset),
286 macros is a size in bytes.
288 The data types for arguments and return values shown
289 in the SYNOPSIS are hints what about is expected in each case.
290 However, since these interfaces are implemented as macros,
291 the compiler won't necessarily catch all type errors
292 if you violate the suggestions.
294 The following program demonstrates the use of some of the macros
295 used for dynamically allocated CPU sets.
306 main(int argc, char *argv[])
313 fprintf(stderr, "Usage: %s <num\-cpus>\\n", argv[0]);
317 num_cpus = atoi(argv[1]);
319 cpusetp = CPU_ALLOC(num_cpus);
320 if (cpusetp == NULL) {
325 size = CPU_ALLOC_SIZE(num_cpus);
327 CPU_ZERO_S(size, cpusetp);
328 for (cpu = 0; cpu < num_cpus; cpu += 2)
329 CPU_SET_S(cpu, size, cpusetp);
331 printf("CPU_COUNT() of set: %d\\n", CPU_COUNT_S(size, cpusetp));
338 On 32-bit platforms with glibc 2.8 and earlier,
340 allocates twice as much space as is required, and
341 .BR CPU_ALLOC_SIZE ()
342 returns a value twice as large as it should.
343 This bug should not affect the semantics of a program,
344 but does result in wasted memory
345 and less efficient operation of the macros that
346 operate on dynamically allocated CPU sets.
347 These bugs are fixed in glibc 2.9.
348 .\" http://sourceware.org/bugzilla/show_bug.cgi?id=7029
350 .BR sched_setaffinity (2),
351 .BR pthread_attr_setaffinity_np (3),
352 .BR pthread_setaffinity_np (3),