iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

perf tools: Fix SMT fallback with large core counts

Browse Source 
strtoull can only read a 64-bit bitmap. On an AMD EPYC core_cpus may look
like:

00000000,00000000,00000000,00000001,00000000,00000000,00000000,00000001

and so the sibling wasn't spotted. Fix by writing a simple hweight string
parser.

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/20211124001231.3277836-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Ian Rogers 2021-11-23 16:12:30 -08:00 committed by Arnaldo Carvalho de Melo
parent 6d18804b96
commit 0ce05781f4
1 changed files with 58 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

68
tools/perf/util/smt.c
View File

@ -5,6 +5,56 @@
#include "api/fs/fs.h"
#include "smt.h"
/**
* hweight_str - Returns the number of bits set in str. Stops at first non-hex
* or ',' character.
*/
static int hweight_str(char *str)
{
int result = 0;
while (*str) {
switch (*str++) {
case '0':
case ',':
break;
case '1':
case '2':
case '4':
case '8':
result++;
break;
case '3':
case '5':
case '6':
case '9':
case 'a':
case 'A':
case 'c':
case 'C':
result += 2;
break;
case '7':
case 'b':
case 'B':
case 'd':
case 'D':
case 'e':
case 'E':
result += 3;
break;
case 'f':
case 'F':
result += 4;
break;
default:
goto done;
}
}
done:
return result;
}
int smt_on(void)
{
static bool cached;
@ -15,9 +65,12 @@ int smt_on(void)
if (cached)
return cached_result;
if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) >= 0)
goto done;
if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) >= 0) {
cached = true;
return cached_result;
}
cached_result = 0;
ncpu = sysconf(_SC_NPROCESSORS_CONF);
for (cpu = 0; cpu < ncpu; cpu++) {
unsigned long long siblings;
@ -35,18 +88,13 @@ int smt_on(void)
continue;
}
/* Entry is hex, but does not have 0x, so need custom parser */
siblings = strtoull(str, NULL, 16);
siblings = hweight_str(str);
free(str);
if (hweight64(siblings) > 1) {
if (siblings > 1) {
cached_result = 1;
cached = true;
break;
}
}
if (!cached) {
cached_result = 0;
done:
cached = true;
}
cached = true;
return cached_result;
}