CPU_SET, CPU_CLR, CPU_ISSET, CPU_ZERO, CPU_COUNT, CPU_AND, CPU_OR, CPU_XOR,
CPU_EQUAL, 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,
CPU_EQUAL_S - macros for manipulating CPU sets
#define _GNU_SOURCE /* feature_test_macros(7) 参照 */
#include <sched.h>
void CPU_ZERO(cpu_set_t *set);
void CPU_SET(int cpu, cpu_set_t *set);
void CPU_CLR(int cpu, cpu_set_t *set);
int CPU_ISSET(int cpu, cpu_set_t *set);
int CPU_COUNT(cpu_set_t *set);
void CPU_AND(cpu_set_t *destset,
cpu_set_t *srcset1, cpu_set_t *srcset2);
void CPU_OR(cpu_set_t *destset,
cpu_set_t *srcset1, cpu_set_t *srcset2);
void CPU_XOR(cpu_set_t *destset,
cpu_set_t *srcset1, cpu_set_t *srcset2);
int CPU_EQUAL(cpu_set_t *set1, cpu_set_t *set2);
cpu_set_t *CPU_ALLOC(int num_cpus);
void CPU_FREE(cpu_set_t *set);
size_t CPU_ALLOC_SIZE(int num_cpus);
void CPU_ZERO_S(size_t setsize, cpu_set_t *set);
void CPU_SET_S(int cpu, size_t setsize, cpu_set_t *set);
void CPU_CLR_S(int cpu, size_t setsize, cpu_set_t *set);
int CPU_ISSET_S(int cpu, size_t setsize, cpu_set_t *set);
int CPU_COUNT_S(size_t setsize, cpu_set_t *set);
void CPU_AND_S(size_t setsize, cpu_set_t *destset,
cpu_set_t *srcset1, cpu_set_t *srcset2);
void CPU_OR_S(size_t setsize, cpu_set_t *destset,
cpu_set_t *srcset1, cpu_set_t *srcset2);
void CPU_XOR_S(size_t setsize, cpu_set_t *destset,
cpu_set_t *srcset1, cpu_set_t *srcset2);
int CPU_EQUAL_S(size_t setsize, cpu_set_t *set1, cpu_set_t *set2);
The
cpu_set_t data structure represents a set of CPUs. CPU sets are used
by
sched_setaffinity(2) and similar interfaces.
The
cpu_set_t data type is implemented as a bitset. However, the data
structure treated as considered opaque: all manipulation of CPU sets should be
done via the macros described in this page.
The following macros are provided to operate on the CPU set
set:
- CPU_ZERO()
- Clears set, so that it contains no CPUs.
- CPU_SET()
- Add CPU cpu to set.
- CPU_CLR()
- Remove CPU cpu from set.
- CPU_ISSET()
- Test to see if CPU cpu is a member of
set.
- CPU_COUNT()
- Return the number of CPUs in set.
Where a
cpu argument is specified, it should not produce side effects,
since the above macros may evaluate the argument more than once.
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. The constant
CPU_SETSIZE (currently 1024) specifies a value one greater than the
maximum CPU number that can be stored in
cpu_set_t.
The following macros perform logical operations on CPU sets:
- CPU_AND()
- Store the intersection of the sets srcset1 and
srcset2 in destset (which may be one of the source
sets).
- CPU_OR()
- Store the union of the sets srcset1 and
srcset2 in destset (which may be one of the source
sets).
- CPU_XOR()
- Store the XOR of the sets srcset1 and srcset2
in destset (which may be one of the source sets). The XOR means the
set of CPUs that are in either srcset1 or srcset2, but not
both.
- CPU_EQUAL()
- Test whether two CPU set contain exactly the same
CPUs.
Dynamically sized CPU sets¶
Because some applications may require the ability to dynamically size CPU sets
(e.g., to allocate sets larger than that defined by the standard
cpu_set_t data type), glibc nowadays provides a set of macros to
support this.
The following macros are used to allocate and deallocate CPU sets:
- CPU_ALLOC()
- Allocate a CPU set large enough to hold CPUs in the range 0
to num_cpus-1.
- CPU_ALLOC_SIZE()
- Return the size in bytes of the CPU set that would be
needed to hold CPUs in the range 0 to num_cpus-1. This macro
provides the value that can be used for the setsize argument in the
CPU_*_S() macros described below.
- CPU_FREE()
- Free a CPU set previously allocated by
CPU_ALLOC().
The macros whose names end with "_S" are the analogs of the similarly
named macros without the suffix. These macros perform the same tasks as their
analogs, but operate on the dynamically allocated CPU set(s) whose size is
setsize bytes.
返り値¶
CPU_ISSET() and
CPU_ISSET_S() return nonzero if
cpu is in
set; otherwise, it returns 0.
CPU_COUNT() and
CPU_COUNT_S() return the number of CPUs in
set.
CPU_EQUAL() and
CPU_EQUAL_S() return nonzero if the two CPU sets
are equal; otherwise it returns 0.
CPU_ALLOC() returns a pointer on success, or NULL on failure. (Errors are
as for
malloc(3).)
CPU_ALLOC_SIZE() returns the number of bytes required to store a CPU set
of the specified cardinality.
The other functions do not return a value.
バージョン¶
The
CPU_ZERO(),
CPU_SET(),
CPU_CLR(), and
CPU_ISSET() macros were added in glibc 2.3.3.
CPU_COUNT() first appeared in glibc 2.6.
CPU_AND(),
CPU_OR(),
CPU_XOR(),
CPU_EQUAL(),
CPU_ALLOC(),
CPU_ALLOC_SIZE(),
CPU_FREE(),
CPU_ZERO_S(),
CPU_SET_S(),
CPU_CLR_S(),
CPU_ISSET_S(),
CPU_AND_S(),
CPU_OR_S(),
CPU_XOR_S(), and
CPU_EQUAL_S() first appeared in glibc 2.7.
These interfaces are Linux-specific.
To duplicate a CPU set, use
memcpy(3).
Since CPU sets are bitsets allocated in units of long words, the actual number
of CPUs in a dynamically allocated CPU set will be rounded up to the next
multiple of
sizeof(unsigned long). An application should consider the
contents of these extra bits to be undefined.
Notwithstanding the similarity in the names, note that the constant
CPU_SETSIZE indicates the number of CPUs in the
cpu_set_t data
type (thus, it is effectively a count of bits in the bitset), while the
setsize argument of the
CPU_*_S() macros is a size in bytes.
The data types for arguments and return values shown in the SYNOPSIS are hints
what about is expected in each case. However, since these interfaces are
implemented as macros, the compiler won't necessarily catch all type errors if
you violate the suggestions.
On 32-bit platforms with glibc 2.8 and earlier,
CPU_ALLOC() allocates
twice as much space as is required, and
CPU_ALLOC_SIZE() returns a
value twice as large as it should. This bug should not affect the semantics of
a program, but does result in wasted memory and less efficient operation of
the macros that operate on dynamically allocated CPU sets. These bugs are
fixed in glibc 2.9.
EXAMPLE¶
The following program demonstrates the use of some of the macros used for
dynamically allocated CPU sets.
#define _GNU_SOURCE
#include <sched.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <assert.h>
int
main(int argc, char *argv[])
{
cpu_set_t *cpusetp;
size_t size;
int num_cpus, cpu;
if (argc < 2) {
fprintf(stderr, "Usage: %s <num-cpus>\n", argv[0]);
exit(EXIT_FAILURE);
}
num_cpus = atoi(argv[1]);
cpusetp = CPU_ALLOC(num_cpus);
if (cpusetp == NULL) {
perror("CPU_ALLOC");
exit(EXIT_FAILURE);
}
size = CPU_ALLOC_SIZE(num_cpus);
CPU_ZERO_S(size, cpusetp);
for (cpu = 0; cpu < num_cpus; cpu += 2)
CPU_SET_S(cpu, size, cpusetp);
printf("CPU_COUNT() of set: %d\n", CPU_COUNT_S(size, cpusetp));
CPU_FREE(cpusetp);
exit(EXIT_SUCCESS);
}
関連項目¶
sched_setaffinity(2),
pthread_attr_setaffinity_np(3),
pthread_setaffinity_np(3),
cpuset(7)
この文書について¶
この man ページは Linux
man-pages
プロジェクトのリリース
3.41 の一部
である。プロジェクトの説明とバグ報告に関する情報は
http://www.kernel.org/doc/man-pages/
に書かれている。