65 lines
2.1 KiB
Diff
65 lines
2.1 KiB
Diff
diff -up man-pages-3.22/man2/sched_setaffinity.2.orig man-pages-3.22/man2/sched_setaffinity.2
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--- man-pages-3.22/man2/sched_setaffinity.2.orig 2009-07-25 08:53:26.000000000 +0200
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+++ man-pages-3.22/man2/sched_setaffinity.2 2009-12-02 15:29:17.000000000 +0100
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@@ -212,6 +212,60 @@ system call returns the size (in bytes)
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.I cpumask_t
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data type that is used internally by the kernel to
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represent the CPU set bit mask.
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+
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+The \fBcpu_set_t\fR affinity mask size provided by glibc only allows for upto
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+1024 CPUs. It is possible to build Linux kernels with greater than 1024
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+CPUs. Any application using the statically sized \fBcpu_set_t\fR will fail
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+with \fBEINVAL\fR on such kernels. It is thus recommended that applications
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+avoid using the statically sized \fBcpu_set_t\fR type, and instead dynamically
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+allocate a mask using the CPU_*_S macros described in the \fBCPU_SET(3)\fR man
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+page. Since it is not possible to determine ahead of time what \fBNR_CPUS\fR
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+value the kernel was built with, applications must be prepared to catch
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+\fBEINVAL\fR, and retry the command with a larger dynamically allocated mask.
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+The example that follows illustrates portable usage.
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+
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+.SH EXAMPLE
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+.nf
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+ #define _GNU_SOURCE
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+
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+ #include <sched.h>
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+ #include <stdio.h>
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+ #include <errno.h>
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+
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+ int main(void)
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+ {
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+ cpu_set_t *mask;
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+ size_t size;
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+ int i;
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+ int nrcpus = 1024;
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+
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+realloc:
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+ mask = CPU_ALLOC(nrcpus);
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+ size = CPU_ALLOC_SIZE(nrcpus);
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+ CPU_ZERO_S(size, mask);
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+ if ( sched_getaffinity(0, size, mask) == -1 ) {
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+ CPU_FREE(mask);
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+ if (errno == EINVAL &&
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+ nrcpus < (1024 << 8)) {
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+ nrcpus = nrcpus << 2;
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+ goto realloc;
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+ }
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+ perror("sched_getaffinity");
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+ return -1;
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+ }
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+
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+ for ( i = 0; i < nrcpus; i++ ) {
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+ if ( CPU_ISSET_S(i, size, mask) ) {
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+ printf("CPU %d is set\\n", (i+1));
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+ }
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+ }
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+
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+ CPU_FREE(mask);
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+
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+ return 0;
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+ }
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+.fi
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+
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.SH "SEE ALSO"
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.BR clone (2),
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.BR getcpu (2),
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