[PATCH v2 2/3] perf tool: fix detecting smt at machines with more than 32 cpus

[Konstantin Khlebnikov]

Cpu bitmap is split into 32 bit words. For system with more than 32 cores
threads are always in different words thus first word never has two bits:
cpu0: "0000,00000100,00000001", cpu 79: "8000,00000080,00000000".

Instead of parsing bitmap read "core_cpus_list" or "thread_siblings_list"
and simply check presence of ',' or '-' in it.

Signed-off-by: Konstantin Khlebnikov <khlebni...@yandex-team.ru>
Fixes: de5077c4e38f ("perf tools: Add utility function to detect SMT status")
---
 tools/perf/util/smt.c |   37 +++++++++++++++++--------------------
 1 file changed, 17 insertions(+), 20 deletions(-)

diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c
index 8481842e9edb..dc37b5abd1c3 100644
--- a/tools/perf/util/smt.c
+++ b/tools/perf/util/smt.c
@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <string.h>
 #include <linux/bitops.h>
 #include "api/fs/fs.h"
 #include "smt.h"
@@ -9,39 +10,35 @@ int smt_on(void)
 {
        static bool cached;
        static int cached_result;
+       int active;
        int cpu;
        int ncpu;
+       char *str = NULL;
+       size_t strlen;
 
        if (cached)
                return cached_result;
 
        ncpu = sysconf(_SC_NPROCESSORS_CONF);
        for (cpu = 0; cpu < ncpu; cpu++) {
-               unsigned long long siblings;
-               char *str;
-               size_t strlen;
                char fn[256];
 
-               snprintf(fn, sizeof fn,
-                       "devices/system/cpu/cpu%d/topology/core_cpus", cpu);
-               if (sysfs__read_str(fn, &str, &strlen) < 0) {
-                       snprintf(fn, sizeof fn,
-                               
"devices/system/cpu/cpu%d/topology/thread_siblings",
-                               cpu);
-                       if (sysfs__read_str(fn, &str, &strlen) < 0)
-                               continue;
-               }
-               /* Entry is hex, but does not have 0x, so need custom parser */
-               siblings = strtoull(str, NULL, 16);
-               free(str);
-               if (hweight64(siblings) > 1) {
-                       cached_result = 1;
-                       cached = true;
+               snprintf(fn, sizeof(fn), "devices/system/cpu/cpu%d/topology/%s",
+                        cpu, "core_cpus_list");
+               if (sysfs__read_str(fn, &str, &strlen) > 0)
+                       break;
+
+               snprintf(fn, sizeof(fn), "devices/system/cpu/cpu%d/topology/%s",
+                        cpu, "thread_siblings_list");
+               if (sysfs__read_str(fn, &str, &strlen) > 0)
                        break;
-               }
        }
+
+       active = str && (strchr(str, ',') != NULL || strchr(str, '-') != NULL);
+       free(str);
+
        if (!cached) {
-               cached_result = 0;
+               cached_result = active;
                cached = true;
        }
        return cached_result;