Messages in this thread Patch in this message | | | Date | Thu, 26 May 2022 21:04:07 -0700 | Subject | [PATCH v2] perf metrics: Add literal for system TSC frequency | From | Ian Rogers <> |
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Such a literal is useful to calculate things like the average frequency [1]. The TSC frequency isn't exposed by sysfs although some experimental drivers look to add it [2]. This change computes the value using the frequency in /proc/cpuinfo which is accurate at least on Intel processors.
v2. Adds warnings to make clear if things have changed/broken on future Intel platforms. It also adds caching and an Intel specific that a value is computed.
[1] https://github.com/intel/perfmon-metrics/blob/5ad9ef7056f31075e8178b9f1fb732af183b2c8d/SKX/metrics/perf/skx_metric_perf.json#L11 [2] https://github.com/trailofbits/tsc_freq_khz
Signed-off-by: Ian Rogers <irogers@google.com> --- tools/perf/tests/expr.c | 15 +++++++++++++ tools/perf/util/expr.c | 50 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 65 insertions(+)
diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c index 5c0032fe93ae..45afe4f24859 100644 --- a/tools/perf/tests/expr.c +++ b/tools/perf/tests/expr.c @@ -1,8 +1,10 @@ // SPDX-License-Identifier: GPL-2.0 #include "util/debug.h" #include "util/expr.h" +#include "util/header.h" #include "util/smt.h" #include "tests.h" +#include <math.h> #include <stdlib.h> #include <string.h> #include <linux/zalloc.h> @@ -69,6 +71,11 @@ static int test__expr(struct test_suite *t __maybe_unused, int subtest __maybe_u double val, num_cpus, num_cores, num_dies, num_packages; int ret; struct expr_parse_ctx *ctx; + bool is_intel = false; + char buf[128]; + + if (!get_cpuid(buf, sizeof(buf))) + is_intel = strstr(buf, "Intel") != NULL; TEST_ASSERT_EQUAL("ids_union", test_ids_union(), 0); @@ -175,6 +182,14 @@ static int test__expr(struct test_suite *t __maybe_unused, int subtest __maybe_u if (num_dies) // Some platforms do not have CPU die support, for example s390 TEST_ASSERT_VAL("#num_dies >= #num_packages", num_dies >= num_packages); + if (is_intel) { + double system_tsc_freq; + + TEST_ASSERT_VAL("#system_tsc_freq", expr__parse(&system_tsc_freq, ctx, + "#system_tsc_freq") == 0); + TEST_ASSERT_VAL("!isnan(#system_tsc_freq)", !isnan(system_tsc_freq)); + } + /* * Source count returns the number of events aggregating in a leader * event including the leader. Check parsing yields an id. diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c index 675f318ce7c1..f33aeb1e6faa 100644 --- a/tools/perf/util/expr.c +++ b/tools/perf/util/expr.c @@ -402,6 +402,51 @@ double expr_id_data__source_count(const struct expr_id_data *data) return data->val.source_count; } +/* + * 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 system_tsc_freq(void) +{ + static double result; + static bool computed; + FILE *cpuinfo; + char *line = NULL; + size_t len = 0; + + if (computed) + return result; + + computed = true; + result = NAN; + 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 (isnan(result)) + pr_err("Failed to find TSC frequency in /proc/cpuinfo"); + + free(line); + fclose(cpuinfo); + return result; +} + double expr__get_literal(const char *literal) { static struct cpu_topology *topology; @@ -417,6 +462,11 @@ double expr__get_literal(const char *literal) goto out; } + if (!strcasecmp("#system_tsc_freq", literal)) { + result = system_tsc_freq(); + goto out; + } + /* * Assume that topology strings are consistent, such as CPUs "0-1" * wouldn't be listed as "0,1", and so after deduplication the number of -- 2.36.1.124.g0e6072fb45-goog
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