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6dd8646939
Following Documentation/ABI/stable/sysfs-devices-system-cpu the /sys/devices/system/cpu/cpuX/topology/core_cpus is deprecated in favor of thread_siblings, so probe thread_siblings before falling back on core_cpus. Signed-off-by: Ian Rogers <irogers@google.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: John Garry <john.garry@huawei.com> Cc: Kajol Jain <kjain@linux.ibm.com> Cc: Kan Liang <kan.liang@linux.intel.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Paul Clarke <pc@us.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Link: https://lore.kernel.org/r/20211124001231.3277836-4-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
100 lines
1.7 KiB
C
100 lines
1.7 KiB
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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/**
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* hweight_str - Returns the number of bits set in str. Stops at first non-hex
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* or ',' character.
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*/
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static int hweight_str(char *str)
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{
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int result = 0;
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while (*str) {
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switch (*str++) {
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case '0':
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case ',':
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break;
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case '1':
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case '2':
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case '4':
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case '8':
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result++;
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break;
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case '3':
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case '5':
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case '6':
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case '9':
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case 'a':
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case 'A':
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case 'c':
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case 'C':
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result += 2;
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break;
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case '7':
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case 'b':
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case 'B':
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case 'd':
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case 'D':
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case 'e':
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case 'E':
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result += 3;
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break;
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case 'f':
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case 'F':
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result += 4;
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break;
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default:
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goto done;
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}
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}
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done:
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return result;
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}
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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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if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) >= 0) {
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cached = true;
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return cached_result;
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}
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cached_result = 0;
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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", cpu);
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if (sysfs__read_str(fn, &str, &strlen) < 0) {
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snprintf(fn, sizeof fn,
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"devices/system/cpu/cpu%d/topology/core_cpus", cpu);
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if (sysfs__read_str(fn, &str, &strlen) < 0)
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continue;
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}
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/* Entry is hex, but does not have 0x, so need custom parser */
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siblings = hweight_str(str);
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free(str);
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if (siblings > 1) {
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cached_result = 1;
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break;
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}
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}
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cached = true;
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return cached_result;
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}
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