CPU_OR(3)

1CPU_SET(3)                 Linux Programmer's Manual                CPU_SET(3)
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NAME

6       CPU_SET,  CPU_CLR,  CPU_ISSET,  CPU_ZERO,  CPU_COUNT,  CPU_AND, CPU_OR,
7       CPU_XOR, CPU_EQUAL,  CPU_ALLOC,  CPU_ALLOC_SIZE,  CPU_FREE,  CPU_SET_S,
8       CPU_CLR_S,  CPU_ISSET_S,  CPU_ZERO_S, CPU_COUNT_S, CPU_AND_S, CPU_OR_S,
9       CPU_XOR_S, CPU_EQUAL_S - macros for manipulating CPU sets
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SYNOPSIS

12       #define _GNU_SOURCE             /* See feature_test_macros(7) */
13       #include <sched.h>
14
15       void CPU_ZERO(cpu_set_t *set);
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17       void CPU_SET(int cpu, cpu_set_t *set);
18       void CPU_CLR(int cpu, cpu_set_t *set);
19       int  CPU_ISSET(int cpu, cpu_set_t *set);
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21       int  CPU_COUNT(cpu_set_t *set);
22
23       void CPU_AND(cpu_set_t *destset,
24                    cpu_set_t *srcset1, cpu_set_t *srcset2);
25       void CPU_OR(cpu_set_t *destset,
26                    cpu_set_t *srcset1, cpu_set_t *srcset2);
27       void CPU_XOR(cpu_set_t *destset,
28                    cpu_set_t *srcset1, cpu_set_t *srcset2);
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30       int  CPU_EQUAL(cpu_set_t *set1, cpu_set_t *set2);
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32       cpu_set_t *CPU_ALLOC(int num_cpus);
33       void CPU_FREE(cpu_set_t *set);
34       size_t CPU_ALLOC_SIZE(int num_cpus);
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36       void CPU_ZERO_S(size_t setsize, cpu_set_t *set);
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38       void CPU_SET_S(int cpu, size_t setsize, cpu_set_t *set);
39       void CPU_CLR_S(int cpu, size_t setsize, cpu_set_t *set);
40       int  CPU_ISSET_S(int cpu, size_t setsize, cpu_set_t *set);
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42       int  CPU_COUNT_S(size_t setsize, cpu_set_t *set);
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44       void CPU_AND_S(size_t setsize, cpu_set_t *destset,
45                    cpu_set_t *srcset1, cpu_set_t *srcset2);
46       void CPU_OR_S(size_t setsize, cpu_set_t *destset,
47                    cpu_set_t *srcset1, cpu_set_t *srcset2);
48       void CPU_XOR_S(size_t setsize, cpu_set_t *destset,
49                    cpu_set_t *srcset1, cpu_set_t *srcset2);
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51       int  CPU_EQUAL_S(size_t setsize, cpu_set_t *set1, cpu_set_t *set2);
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DESCRIPTION

54       The cpu_set_t data structure represents a set of CPUs.   CPU  sets  are
55       used by sched_setaffinity(2) and similar interfaces.
56
57       The  cpu_set_t data type is implemented as a bitset.  However, the data
58       structure treated as considered opaque: all manipulation  of  CPU  sets
59       should be done via the macros described in this page.
60
61       The following macros are provided to operate on the CPU set set:
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63       CPU_ZERO()       Clears set, so that it contains no CPUs.
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65       CPU_SET()        Add CPU cpu to set.
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67       CPU_CLR()        Remove CPU cpu from set.
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69       CPU_ISSET()      Test to see if CPU cpu is a member of set.
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71       CPU_COUNT()      Return the number of CPUs in set.
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73       Where  a cpu argument is specified, it should not produce side effects,
74       since the above macros may evaluate the argument more than once.
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76       The first available CPU on the system corresponds to a cpu value of  0,
77       the  next CPU corresponds to a cpu value of 1, and so on.  The constant
78       CPU_SETSIZE (currently 1024) specifies a value  one  greater  than  the
79       maximum CPU number that can be stored in cpu_set_t.
80
81       The following macros perform logical operations on CPU sets:
82
83       CPU_AND()        Store the intersection of the sets srcset1 and srcset2
84                        in destset (which may be one of the source sets).
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86       CPU_OR()         Store the union of the sets  srcset1  and  srcset2  in
87                        destset (which may be one of the source sets).
88
89       CPU_XOR()        Store the XOR of the sets srcset1 and srcset2 in dest‐
90                        set (which may be one of the source  sets).   The  XOR
91                        means  the  set  of CPUs that are in either srcset1 or
92                        srcset2, but not both.
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94       CPU_EQUAL()      Test whether two CPU  set  contain  exactly  the  same
95                        CPUs.
96
97   Dynamically sized CPU sets
98       Because  some  applications may require the ability to dynamically size
99       CPU sets (e.g., to allocate sets larger than that defined by the  stan‐
100       dard  cpu_set_t  data type), glibc nowadays provides a set of macros to
101       support this.
102
103       The following macros are used to allocate and deallocate CPU sets:
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105       CPU_ALLOC()      Allocate a CPU set large enough to hold  CPUs  in  the
106                        range 0 to num_cpus-1.
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108       CPU_ALLOC_SIZE() Return  the size in bytes of the CPU set that would be
109                        needed to hold CPUs in  the  range  0  to  num_cpus-1.
110                        This macro provides the value that can be used for the
111                        setsize argument in  the  CPU_*_S()  macros  described
112                        below.
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114       CPU_FREE()       Free a CPU set previously allocated by CPU_ALLOC().
115
116       The  macros  whose names end with "_S" are the analogs of the similarly
117       named macros without the suffix.  These macros perform the  same  tasks
118       as  their  analogs, but operate on the dynamically allocated CPU set(s)
119       whose size is setsize bytes.
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RETURN VALUE

122       CPU_ISSET() and CPU_ISSET_S() return nonzero if cpu is in  set;  other‐
123       wise, it returns 0.
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125       CPU_COUNT() and CPU_COUNT_S() return the number of CPUs in set.
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127       CPU_EQUAL()  and  CPU_EQUAL_S()  return nonzero if the two CPU sets are
128       equal; otherwise it returns 0.
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130       CPU_ALLOC() returns a pointer on success, or NULL on failure.   (Errors
131       are as for malloc(3).)
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133       CPU_ALLOC_SIZE()  returns  the  number of bytes required to store a CPU
134       set of the specified cardinality.
135
136       The other functions do not return a value.
137

VERSIONS

139       The CPU_ZERO(), CPU_SET(), CPU_CLR(), and CPU_ISSET() macros were added
140       in glibc 2.3.3.
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142       CPU_COUNT() first appeared in glibc 2.6.
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144       CPU_AND(),     CPU_OR(),     CPU_XOR(),    CPU_EQUAL(),    CPU_ALLOC(),
145       CPU_ALLOC_SIZE(), CPU_FREE(), CPU_ZERO_S(),  CPU_SET_S(),  CPU_CLR_S(),
146       CPU_ISSET_S(),  CPU_AND_S(), CPU_OR_S(), CPU_XOR_S(), and CPU_EQUAL_S()
147       first appeared in glibc 2.7.
148

CONFORMING TO

150       These interfaces are Linux-specific.
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NOTES

153       To duplicate a CPU set, use memcpy(3).
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155       Since CPU sets are bitsets allocated in units of long words, the actual
156       number of CPUs in a dynamically allocated CPU set will be rounded up to
157       the next multiple of sizeof(unsigned long).  An application should con‐
158       sider the contents of these extra bits to be undefined.
159
160       Notwithstanding  the  similarity  in  the names, note that the constant
161       CPU_SETSIZE indicates the number of CPUs in  the  cpu_set_t  data  type
162       (thus, it is effectively a count of bits in the bitset), while the set‐
163       size argument of the CPU_*_S() macros is a size in bytes.
164
165       The data types for arguments and return values shown  in  the  SYNOPSIS
166       are  hints  what  about is expected in each case.  However, since these
167       interfaces are implemented as macros, the  compiler  won't  necessarily
168       catch all type errors if you violate the suggestions.
169

BUGS

171       On  32-bit  platforms with glibc 2.8 and earlier, CPU_ALLOC() allocates
172       twice as much space as is  required,  and  CPU_ALLOC_SIZE()  returns  a
173       value  twice  as  large  as  it should.  This bug should not affect the
174       semantics of a program, but does result in wasted memory and less effi‐
175       cient operation of the macros that operate on dynamically allocated CPU
176       sets.  These bugs are fixed in glibc 2.9.
177

EXAMPLE

179       The following program demonstrates the use of some of the  macros  used
180       for dynamically allocated CPU sets.
181
182       #define _GNU_SOURCE
183       #include <sched.h>
184       #include <stdlib.h>
185       #include <unistd.h>
186       #include <stdio.h>
187       #include <assert.h>
188
189       int
190       main(int argc, char *argv[])
191       {
192           cpu_set_t *cpusetp;
193           size_t size;
194           int num_cpus, cpu;
195
196           if (argc < 2) {
197               fprintf(stderr, "Usage: %s <num-cpus>\n", argv[0]);
198               exit(EXIT_FAILURE);
199           }
200
201           num_cpus = atoi(argv[1]);
202
203           cpusetp = CPU_ALLOC(num_cpus);
204           if (cpusetp == NULL) {
205               perror("CPU_ALLOC");
206               exit(EXIT_FAILURE);
207           }
208
209           size = CPU_ALLOC_SIZE(num_cpus);
210
211           CPU_ZERO_S(size, cpusetp);
212           for (cpu = 0; cpu < num_cpus; cpu += 2)
213               CPU_SET_S(cpu, size, cpusetp);
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215           printf("CPU_COUNT() of set:    %d\n", CPU_COUNT_S(size, cpusetp));
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217           CPU_FREE(cpusetp);
218           exit(EXIT_SUCCESS);
219       }
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COLOPHON

226       This page is part of release 3.53 of the Linux  man-pages  project.   A
227       description  of  the project, and information about reporting bugs, can
228       be found at http://www.kernel.org/doc/man-pages/.
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232Linux                             2012-03-15                        CPU_SET(3)