linux-kernel - [PATCH v4 0/3] Add arch TSC frequency information

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Date:   Mon, 18 Jul 2022 09:43:09 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     perry.taylor@...el.com, caleb.biggers@...el.com,
        kshipra.bopardikar@...el.com,
        Kan Liang <kan.liang@...ux.intel.com>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Andi Kleen <ak@...ux.intel.com>,
        James Clark <james.clark@....com>,
        John Garry <john.garry@...wei.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Cc:     Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>
Subject: [PATCH v4 0/3] Add arch TSC frequency information

The first patch adds the #system_tsc_freq literal to expr.c and
computes it via cpuid. The second patches adds support for "older"
processors by computing the value via /proc/cpuinfo. The third patch
adds a test then the computation looks somewhat sensible.

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].

[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

v4. Modified the patch order and separated out the test.
v3. Added the cpuid approach from Kan Liang.
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.

Ian Rogers (2):
  perf tsc: Add cpuinfo fall back for arch_get_tsc_freq
  perf test: Add test for #system_tsc_freq in metrics

Kan Liang (1):
  perf tsc: Add arch TSC frequency information

 tools/perf/arch/x86/util/cpuid.h  | 34 ++++++++++++++
 tools/perf/arch/x86/util/header.c | 27 +++++------
 tools/perf/arch/x86/util/tsc.c    | 77 +++++++++++++++++++++++++++++++
 tools/perf/tests/expr.c           | 13 ++++++
 tools/perf/util/expr.c            | 13 ++++++
 tools/perf/util/tsc.h             |  1 +
 6 files changed, 149 insertions(+), 16 deletions(-)
 create mode 100644 tools/perf/arch/x86/util/cpuid.h

-- 
2.37.0.170.g444d1eabd0-goog