Message-ID: <CAP-5=fVPw5wJtVR0fxU-7drXg34vNrBsEzurfcLLvC+wFPMAAg@mail.gmail.com>
Date: Wed, 4 Dec 2024 22:33:49 -0800
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: 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@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	James Clark <james.clark@...aro.org>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, 
	akanksha@...ux.ibm.com, maddy@...ux.ibm.com, atrajeev@...ux.vnet.ibm.com, 
	kjain@...ux.ibm.com, disgoel@...ux.vnet.ibm.com, hbathini@...ux.ibm.com
Subject: Re: [PATCH v1] perf test expr: Fix system_tsc_freq for only x86

On Wed, Dec 4, 2024 at 9:47 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> Hi Ian,
>
> On Wed, Dec 04, 2024 at 06:23:05PM -0800, Ian Rogers wrote:
> > The refactoring of tool PMU events to have a PMU then adding the expr
> > literals to the tool PMU made it so that the literal system_tsc_freq
> > was only supported on x86. Update the test expectations to match -
> > namely the parsing is x86 specific and only yields a non-zero value on
> > Intel.
> >
> > Fixes: 609aa2667f67 ("perf tool_pmu: Switch to standard pmu functions and json descriptions")
> > Reported-by: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
> > Closes: https://lore.kernel.org/linux-perf-users/20241022140156.98854-1-atrajeev@linux.vnet.ibm.com/
> > Co-developed-by: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
>
> It failed on my VM.
>
>   root@...64-vm:~/build# ./perf test -v 7
>   --- start ---
>   test child forked, pid 2096
>   Using CPUID 0x00000000000f0510
>   division by zero
>   syntax error
>   Unrecognized literal '#system_tsc_freq'FAILED tests/expr.c:253 #system_tsc_freq == 0
>   ---- end(-1) ----
>     7: Simple expression parser                                        : FAILED!

I'll need to check this. The test is looking for parsing failures, so
it's confusing to me expr__parse is returning 0. I was testing on x86
but disabling the literal in the tool PMU.

> > ---
> >  tools/perf/tests/expr.c | 19 ++++++++++++-------
> >  1 file changed, 12 insertions(+), 7 deletions(-)
> >
> > diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
> > index 41ff1affdfcd..726cf8d4da28 100644
> > --- a/tools/perf/tests/expr.c
> > +++ b/tools/perf/tests/expr.c
> > @@ -75,14 +75,12 @@ static int test__expr(struct test_suite *t __maybe_unused, int subtest __maybe_u
> >       double val, num_cpus_online, num_cpus, num_cores, num_dies, num_packages;
> >       int ret;
> >       struct expr_parse_ctx *ctx;
> > -     bool is_intel = false;
> >       char strcmp_cpuid_buf[256];
> >       struct perf_cpu cpu = {-1};
> >       char *cpuid = get_cpuid_allow_env_override(cpu);
> >       char *escaped_cpuid1, *escaped_cpuid2;
> >
> >       TEST_ASSERT_VAL("get_cpuid", cpuid);
> > -     is_intel = strstr(cpuid, "Intel") != NULL;
> >
> >       TEST_ASSERT_EQUAL("ids_union", test_ids_union(), 0);
> >
> > @@ -245,12 +243,19 @@ 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);
> >
> > -     TEST_ASSERT_VAL("#system_tsc_freq", expr__parse(&val, ctx, "#system_tsc_freq") == 0);
> > -     if (is_intel)
> > -             TEST_ASSERT_VAL("#system_tsc_freq > 0", val > 0);
> > -     else
> > -             TEST_ASSERT_VAL("#system_tsc_freq == 0", fpclassify(val) == FP_ZERO);
> >
> > +     if (expr__parse(&val, ctx, "#system_tsc_freq") == 0) {
> > +             bool is_intel = strstr(cpuid, "Intel") != NULL;
> > +
> > +             if (is_intel)
> > +                     TEST_ASSERT_VAL("#system_tsc_freq > 0", val > 0);
>
> Also Sasha reported that some (Intel?) guest machine doesn't have TSC
> frequency.

I think, unfortunately, this is working as intended. Intel metrics use
#system_tsc_freq in metrics for most models:
```
$ grep -ril system_tsc_freq tools/perf/pmu-events/arch/x86/
tools/perf/pmu-events/arch/x86/emeraldrapids/emr-metrics.json
tools/perf/pmu-events/arch/x86/broadwellx/bdx-metrics.json
tools/perf/pmu-events/arch/x86/haswellx/hsx-metrics.json
tools/perf/pmu-events/arch/x86/grandridge/grr-metrics.json
tools/perf/pmu-events/arch/x86/icelakex/icx-metrics.json
tools/perf/pmu-events/arch/x86/sierraforest/srf-metrics.json
tools/perf/pmu-events/arch/x86/skylakex/skx-metrics.json
tools/perf/pmu-events/arch/x86/cascadelakex/clx-metrics.json
tools/perf/pmu-events/arch/x86/sapphirerapids/spr-metrics.json
```
The code to generate the TSC frequency uses the CPUID leaf
information, but this can be disabled by the host operating system for
guest operating systems. The fallback logic using `/proc/cpuinfo` is
intended for older models and it appears the more recent formatting
won't be parse-able by perf. The host has also likely disabled the
information if the CPUID leaf is hidden. So the test is correctly
failing because metrics using #system_tsc_freq would be broken inside
the guest OS. Kan was involved in the conversation when the literal
was added and this was the best we could do.

Thanks,
Ian

> > +             else
> > +                     TEST_ASSERT_VAL("#system_tsc_freq == 0", fpclassify(val) == FP_ZERO);
> > +     } else {
> > +#if defined(__i386__) || defined(__x86_64__)
> > +             TEST_ASSERT_VAL("#system_tsc_freq unsupported", 0);
> > +#endif
> > +     }
> >       /*
> >        * Source count returns the number of events aggregating in a leader
> >        * event including the leader. Check parsing yields an id.
> > --
> > 2.47.0.338.g60cca15819-goog
> >

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