diff options
Diffstat (limited to '')
| -rw-r--r-- | man3/CPU_SET.3 | 348 |
1 files changed, 348 insertions, 0 deletions
diff --git a/man3/CPU_SET.3 b/man3/CPU_SET.3 new file mode 100644 index 0000000..aa5d71d --- /dev/null +++ b/man3/CPU_SET.3 @@ -0,0 +1,348 @@ +.\" Copyright (C) 2006 Michael Kerrisk +.\" and Copyright (C) 2008 Linux Foundation, written by Michael Kerrisk +.\" <mtk.manpages@gmail.com> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.TH CPU_SET 3 2023-05-03 "Linux man-pages 6.05.01" +.SH NAME +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 +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */" +.B #include <sched.h> +.PP +.BI "void CPU_ZERO(cpu_set_t *" set ); +.PP +.BI "void CPU_SET(int " cpu ", cpu_set_t *" set ); +.BI "void CPU_CLR(int " cpu ", cpu_set_t *" set ); +.BI "int CPU_ISSET(int " cpu ", cpu_set_t *" set ); +.PP +.BI "int CPU_COUNT(cpu_set_t *" set ); +.PP +.BI "void CPU_AND(cpu_set_t *" destset , +.BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 ); +.BI "void CPU_OR(cpu_set_t *" destset , +.BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 ); +.BI "void CPU_XOR(cpu_set_t *" destset , +.BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 ); +.PP +.BI "int CPU_EQUAL(cpu_set_t *" set1 ", cpu_set_t *" set2 ); +.PP +.BI "cpu_set_t *CPU_ALLOC(int " num_cpus ); +.BI "void CPU_FREE(cpu_set_t *" set ); +.BI "size_t CPU_ALLOC_SIZE(int " num_cpus ); +.PP +.BI "void CPU_ZERO_S(size_t " setsize ", cpu_set_t *" set ); +.PP +.BI "void CPU_SET_S(int " cpu ", size_t " setsize ", cpu_set_t *" set ); +.BI "void CPU_CLR_S(int " cpu ", size_t " setsize ", cpu_set_t *" set ); +.BI "int CPU_ISSET_S(int " cpu ", size_t " setsize ", cpu_set_t *" set ); +.PP +.BI "int CPU_COUNT_S(size_t " setsize ", cpu_set_t *" set ); +.PP +.BI "void CPU_AND_S(size_t " setsize ", cpu_set_t *" destset , +.BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 ); +.BI "void CPU_OR_S(size_t " setsize ", cpu_set_t *" destset , +.BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 ); +.BI "void CPU_XOR_S(size_t " setsize ", cpu_set_t *" destset , +.BI " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 ); +.PP +.BI "int CPU_EQUAL_S(size_t " setsize ", cpu_set_t *" set1 \ +", cpu_set_t *" set2 ); +.fi +.SH DESCRIPTION +The +.I cpu_set_t +data structure represents a set of CPUs. +CPU sets are used by +.BR sched_setaffinity (2) +and similar interfaces. +.PP +The +.I cpu_set_t +data type is implemented as a bit mask. +However, the data structure should be treated as opaque: +all manipulation of CPU sets should be done via the macros +described in this page. +.PP +The following macros are provided to operate on the CPU set +.IR set : +.TP +.BR CPU_ZERO () +Clears +.IR set , +so that it contains no CPUs. +.TP +.BR CPU_SET () +Add CPU +.I cpu +to +.IR set . +.TP +.BR CPU_CLR () +Remove CPU +.I cpu +from +.IR set . +.TP +.BR CPU_ISSET () +Test to see if CPU +.I cpu +is a member of +.IR set . +.TP +.BR CPU_COUNT () +Return the number of CPUs in +.IR set . +.PP +Where a +.I cpu +argument is specified, it should not produce side effects, +since the above macros may evaluate the argument more than once. +.PP +The first CPU on the system corresponds to a +.I cpu +value of 0, the next CPU corresponds to a +.I cpu +value of 1, and so on. +No assumptions should be made about particular CPUs being +available, or the set of CPUs being contiguous, since CPUs can +be taken offline dynamically or be otherwise absent. +The constant +.B CPU_SETSIZE +(currently 1024) specifies a value one greater than the maximum CPU +number that can be stored in +.IR cpu_set_t . +.PP +The following macros perform logical operations on CPU sets: +.TP +.BR CPU_AND () +Store the intersection of the sets +.I srcset1 +and +.I srcset2 +in +.I destset +(which may be one of the source sets). +.TP +.BR CPU_OR () +Store the union of the sets +.I srcset1 +and +.I srcset2 +in +.I destset +(which may be one of the source sets). +.TP +.BR CPU_XOR () +Store the XOR of the sets +.I srcset1 +and +.I srcset2 +in +.I destset +(which may be one of the source sets). +The XOR means the set of CPUs that are in either +.I srcset1 +or +.IR srcset2 , +but not both. +.TP +.BR CPU_EQUAL () +Test whether two CPU set contain exactly the same CPUs. +.SS 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 +.I cpu_set_t +data type), glibc nowadays provides a set of macros to support this. +.PP +The following macros are used to allocate and deallocate CPU sets: +.TP +.BR CPU_ALLOC () +Allocate a CPU set large enough to hold CPUs +in the range 0 to +.IR num_cpus\-1 . +.TP +.BR CPU_ALLOC_SIZE () +Return the size in bytes of the CPU set that would be needed to +hold CPUs in the range 0 to +.IR num_cpus\-1 . +This macro provides the value that can be used for the +.I setsize +argument in the +.BR CPU_*_S () +macros described below. +.TP +.BR CPU_FREE () +Free a CPU set previously allocated by +.BR CPU_ALLOC (). +.PP +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 +.I setsize +bytes. +.SH RETURN VALUE +.BR CPU_ISSET () +and +.BR CPU_ISSET_S () +return nonzero if +.I cpu +is in +.IR set ; +otherwise, it returns 0. +.PP +.BR CPU_COUNT () +and +.BR CPU_COUNT_S () +return the number of CPUs in +.IR set . +.PP +.BR CPU_EQUAL () +and +.BR CPU_EQUAL_S () +return nonzero if the two CPU sets are equal; otherwise they return 0. +.PP +.BR CPU_ALLOC () +returns a pointer on success, or NULL on failure. +(Errors are as for +.BR malloc (3).) +.PP +.BR CPU_ALLOC_SIZE () +returns the number of bytes required to store a +CPU set of the specified cardinality. +.PP +The other functions do not return a value. +.SH STANDARDS +Linux. +.SH HISTORY +The +.BR CPU_ZERO (), +.BR CPU_SET (), +.BR CPU_CLR (), +and +.BR CPU_ISSET () +macros were added in glibc 2.3.3. +.PP +.BR CPU_COUNT () +first appeared in glibc 2.6. +.PP +.BR CPU_AND (), +.BR CPU_OR (), +.BR CPU_XOR (), +.BR CPU_EQUAL (), +.BR CPU_ALLOC (), +.BR CPU_ALLOC_SIZE (), +.BR CPU_FREE (), +.BR CPU_ZERO_S (), +.BR CPU_SET_S (), +.BR CPU_CLR_S (), +.BR CPU_ISSET_S (), +.BR CPU_AND_S (), +.BR CPU_OR_S (), +.BR CPU_XOR_S (), +and +.BR CPU_EQUAL_S () +first appeared in glibc 2.7. +.SH NOTES +To duplicate a CPU set, use +.BR memcpy (3). +.PP +Since CPU sets are bit masks 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 +.IR "sizeof(unsigned long)" . +An application should consider the contents of these extra bits +to be undefined. +.PP +Notwithstanding the similarity in the names, +note that the constant +.B CPU_SETSIZE +indicates the number of CPUs in the +.I cpu_set_t +data type (thus, it is effectively a count of the bits in the bit mask), +while the +.I setsize +argument of the +.BR CPU_*_S () +macros is a size in bytes. +.PP +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. +.SH BUGS +On 32-bit platforms with glibc 2.8 and earlier, +.BR CPU_ALLOC () +allocates twice as much space as is required, and +.BR 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. +.\" http://sourceware.org/bugzilla/show_bug.cgi?id=7029 +.SH EXAMPLES +The following program demonstrates the use of some of the macros +used for dynamically allocated CPU sets. +.PP +.\" SRC BEGIN (CPU_SET.c) +.EX +#define _GNU_SOURCE +#include <sched.h> +#include <stdio.h> +#include <stdlib.h> +#include <unistd.h> +\& +#include <assert.h> +\& +int +main(int argc, char *argv[]) +{ + cpu_set_t *cpusetp; + size_t size, num_cpus; +\& + if (argc < 2) { + fprintf(stderr, "Usage: %s <num\-cpus>\en", 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 (size_t cpu = 0; cpu < num_cpus; cpu += 2) + CPU_SET_S(cpu, size, cpusetp); +\& + printf("CPU_COUNT() of set: %d\en", CPU_COUNT_S(size, cpusetp)); +\& + CPU_FREE(cpusetp); + exit(EXIT_SUCCESS); +} +.EE +.\" SRC END +.SH SEE ALSO +.BR sched_setaffinity (2), +.BR pthread_attr_setaffinity_np (3), +.BR pthread_setaffinity_np (3), +.BR cpuset (7) |