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perf evsel: Fix missing exclude_{host,guest} setting

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The current logic for the perf missing feature has a bug that it can
wrongly clear some modifiers like G or H.  Actually some PMUs don't
support any filtering or exclusion while others do.  But we check it as
a global feature.

For example, the cycles event can have 'G' modifier to enable it only in
the guest mode on x86.  When you don't run any VMs it'll return 0.

  # perf stat -a -e cycles:G sleep 1

    Performance counter stats for 'system wide':

                    0      cycles:G

          1.000721670 seconds time elapsed

But when it's used with other pmu events that don't support G modifier,
it'll be reset and return non-zero values.

  # perf stat -a -e cycles:G,msr/tsc/ sleep 1

    Performance counter stats for 'system wide':

          538,029,960      cycles:G
       16,924,010,738      msr/tsc/

          1.001815327 seconds time elapsed

This is because of the missing feature detection logic being global.
Add a hashmap to set pmu-specific exclude_host/guest features.

Committer notes:

Fix 'perf test python' by adding a stub for evsel__find_pmu() in
tools/perf/util/python.c, document that it is used so far only for the
above reasons so that if anybody needs this in the python binding
usecases, we can revisit this.

Reported-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Link: http://lore.kernel.org/lkml/20211105205847.120950-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim
2021-11-05 13:58:47 -07:00
committed by Arnaldo Carvalho de Melo
parent 88c42f4d6c
commit 3500eeebed
4 changed files with 42 additions and 5 deletions
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12
tools/perf/util/python.c
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@@ -69,6 +69,18 @@ void perf_stat__collect_metric_expr(struct evlist *evsel_list)
{
}
/*
* This one is needed not to drag the PMU bandwagon, jevents generated
* pmu_sys_event_tables, etc and evsel__find_pmu() is used so far just for
* doing per PMU perf_event_attr.exclude_guest handling, not really needed, so
* far, for the perf python binding known usecases, revisit if this become
* necessary.
*/
struct perf_pmu *evsel__find_pmu(struct evsel *evsel __maybe_unused)
{
return NULL;
}
/*
* Add this one here not to drag util/metricgroup.c
*/