Re: [PATCH v1] perf test switch-tracking: Fix hybrid cpu-cycles and spin timing

[sashiko-bot@kernel.org]

> On hybrid systems, parse_event(evlist, "cpu-cycles:u") creates multiple
> evsels (e.g. cpu_atom/cpu-cycles/ and cpu_core/cpu-cycles/), but
> test__switch_tracking() only configured, enabled/disabled, and checked
> evlist__last(evlist). If the test process ran on another core PMU during
> one of the spin phases, the tracked evsel recorded no samples and the
> test failed with 'Missing cycles events'. Additionally, the other core
> PMU evsels did not have PERF_SAMPLE_TIME set, which add_event() missed
> because __evsel__parse_sample() initializes sample.time to -1ULL rather
> than 0.
> 
> Use evsel__match(evsel, HARDWARE, HW_CPU_CYCLES) to configure,
> enable/disable, and check all cycles evsels created by parse_event(),
> check for sample.time == -1ULL in add_event(), and use
> CLOCK_THREAD_CPUTIME_ID in spin_sleep() so preemption under load does
> not finish the 50ms spin without on-CPU cycles.
> 
> Fixes: 94f9eb95d954 ("perf pmus: Remove perf_pmus__has_hybrid")
> Signed-off-by: Ian Rogers <irogers@google.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261025215056.1228120-1-irogers@google.com?part=1