Commit 3500eeeb authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
Browse files

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



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: default avatarStephane Eranian <eranian@google.com>
Signed-off-by: default avatarNamhyung 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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 88c42f4d

tools/perf/util/evsel.c

+22 −5
Original line number Diff line number Diff line
@@ -1824,7 +1824,7 @@ static void evsel__disable_missing_features(struct evsel *evsel) 
		evsel->open_flags &= ~(unsigned long)PERF_FLAG_FD_CLOEXEC;

	if (perf_missing_features.mmap2)

		evsel->core.attr.mmap2 = 0;

	if (perf_missing_features.exclude_guest)

	if (evsel->pmu && evsel->pmu->missing_features.exclude_guest)

		evsel->core.attr.exclude_guest = evsel->core.attr.exclude_host = 0;

	if (perf_missing_features.lbr_flags)

		evsel->core.attr.branch_sample_type &= ~(PERF_SAMPLE_BRANCH_NO_FLAGS |
@@ -1917,10 +1917,27 @@ bool evsel__detect_missing_features(struct evsel *evsel) 
		perf_missing_features.mmap2 = true;

		pr_debug2_peo("switching off mmap2\n");

		return true;

	} else if (!perf_missing_features.exclude_guest &&

		   (evsel->core.attr.exclude_guest || evsel->core.attr.exclude_host)) {

	} else if ((evsel->core.attr.exclude_guest || evsel->core.attr.exclude_host) &&

		   (evsel->pmu == NULL || evsel->pmu->missing_features.exclude_guest)) {

		if (evsel->pmu == NULL) {

			evsel->pmu = evsel__find_pmu(evsel);

			if (evsel->pmu)

				evsel->pmu->missing_features.exclude_guest = true;

			else {

				/* we cannot find PMU, disable attrs now */

				evsel->core.attr.exclude_host = false;

				evsel->core.attr.exclude_guest = false;

			}

		}



		if (evsel->exclude_GH) {

			pr_debug2_peo("PMU has no exclude_host/guest support, bailing out\n");

			return false;

		}

		if (!perf_missing_features.exclude_guest) {

			perf_missing_features.exclude_guest = true;

			pr_debug2_peo("switching off exclude_guest, exclude_host\n");

		}

		return true;

	} else if (!perf_missing_features.sample_id_all) {

		perf_missing_features.sample_id_all = true;

tools/perf/util/evsel.h

+4 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ struct target; 
struct hashmap;

struct bperf_leader_bpf;

struct bperf_follower_bpf;

struct perf_pmu;



typedef int (evsel__sb_cb_t)(union perf_event *event, void *data);
@@ -153,6 +154,9 @@ struct evsel { 
	};

	unsigned long		open_flags;

	int			precise_ip_original;



	/* for missing_features */

	struct perf_pmu		*pmu;

};



struct perf_missing_features {

tools/perf/util/pmu.h

+4 −0
Original line number Diff line number Diff line
@@ -49,6 +49,10 @@ struct perf_pmu { 
	struct list_head caps;    /* HEAD struct perf_pmu_caps -> list */

	struct list_head list;    /* ELEM */

	struct list_head hybrid_list;



	struct {

		bool exclude_guest;

	} missing_features;

};



extern struct perf_pmu perf_pmu__fake;

tools/perf/util/python.c

+12 −0
Original line number Diff line number Diff line
@@ -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

 */