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perf tsc: Add cpuinfo fall back for arch_get_tsc_freq()

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The CPUID method of arch_get_tsc_freq fails for older Intel processors,
such as Skylake. Compute using /proc/cpuinfo.

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Caleb Biggers <caleb.biggers@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Kshipra Bopardikar <kshipra.bopardikar@intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Perry Taylor <perry.taylor@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20220718164312.3994191-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Ian Rogers 2022-07-18 09:43:11 -07:00 committed by Arnaldo Carvalho de Melo
parent bc2373a58a
commit 1276ade6a5
1 changed files with 48 additions and 4 deletions
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52
tools/perf/arch/x86/util/tsc.c
View File

@ -1,7 +1,9 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <math.h>
#include <string.h>
#include "../../../util/debug.h"
#include "../../../util/tsc.h"
#include "cpuid.h"
@ -14,6 +16,44 @@ u64 rdtsc(void)
return low | ((u64)high) << 32;
}
/*
* Derive the TSC frequency in Hz from the /proc/cpuinfo, for example:
* ...
* model name : Intel(R) Xeon(R) Gold 6154 CPU @ 3.00GHz
* ...
* will return 3000000000.
*/
static double cpuinfo_tsc_freq(void)
{
double result = 0;
FILE *cpuinfo;
char *line = NULL;
size_t len = 0;
cpuinfo = fopen("/proc/cpuinfo", "r");
if (!cpuinfo) {
pr_err("Failed to read /proc/cpuinfo for TSC frequency");
return NAN;
}
while (getline(&line, &len, cpuinfo) > 0) {
if (!strncmp(line, "model name", 10)) {
char *pos = strstr(line + 11, " @ ");
if (pos && sscanf(pos, " @ %lfGHz", &result) == 1) {
result *= 1000000000;
goto out;
}
}
}
out:
if (fpclassify(result) == FP_ZERO)
pr_err("Failed to find TSC frequency in /proc/cpuinfo");
free(line);
fclose(cpuinfo);
return result;
}
double arch_get_tsc_freq(void)
{
unsigned int a, b, c, d, lvl;
@ -33,13 +73,17 @@ double arch_get_tsc_freq(void)
* Don't support Time Stamp Counter and
* Nominal Core Crystal Clock Information Leaf.
*/
if (lvl < 0x15)
return 0;
if (lvl < 0x15) {
tsc = cpuinfo_tsc_freq();
return tsc;
}
cpuid(0x15, 0, &a, &b, &c, &d);
/* TSC frequency is not enumerated */
if (!a || !b || !c)
return 0;
if (!a || !b || !c) {
tsc = cpuinfo_tsc_freq();
return tsc;
}
tsc = (double)c * (double)b / (double)a;
return tsc;