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de5077c4e3
Add an smt_on() function to return if SMT is enabled or disabled. Used in the next patch. Signed-off-by: Andi Kleen <ak@linux.intel.com> Acked-by: Jiri Olsa <jolsa@kernel.org> Link: http://lkml.kernel.org/r/20170811232634.30465-7-andi@firstfloor.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
45 lines
845 B
C
45 lines
845 B
C
#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <linux/bitops.h>
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#include "api/fs/fs.h"
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#include "smt.h"
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int smt_on(void)
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{
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static bool cached;
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static int cached_result;
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int cpu;
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int ncpu;
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if (cached)
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return cached_result;
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ncpu = sysconf(_SC_NPROCESSORS_CONF);
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for (cpu = 0; cpu < ncpu; cpu++) {
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unsigned long long siblings;
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char *str;
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size_t strlen;
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char fn[256];
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snprintf(fn, sizeof fn,
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"devices/system/cpu/cpu%d/topology/thread_siblings",
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cpu);
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if (sysfs__read_str(fn, &str, &strlen) < 0)
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continue;
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/* Entry is hex, but does not have 0x, so need custom parser */
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siblings = strtoull(str, NULL, 16);
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free(str);
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if (hweight64(siblings) > 1) {
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cached_result = 1;
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cached = true;
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break;
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}
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}
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if (!cached) {
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cached_result = 0;
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cached = true;
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}
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return cached_result;
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}
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