Messages in this thread | | | Date | Tue, 26 Oct 2021 20:31:59 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH v2] perf evsel: Fix missing exclude_{host,guest} setting |
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On Mon, Oct 25, 2021 at 09:33:51PM -0700, Namhyung Kim wrote: > 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. > > Reported-by: Stephane Eranian <eranian@google.com> > Signed-off-by: Namhyung Kim <namhyung@kernel.org> > --- > v2 changes) > * change to enum perf_missing_pmu_features > * pass NULL to hashmap__find() to skip checking > * add a blank line after declaration > > tools/perf/util/evsel.c | 47 +++++++++++++++++++++++++++++++++++------ > tools/perf/util/evsel.h | 7 ++++++ > 2 files changed, 48 insertions(+), 6 deletions(-) > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > index dbfeceb2546c..f33801b4615d 100644 > --- a/tools/perf/util/evsel.c > +++ b/tools/perf/util/evsel.c > @@ -1434,6 +1434,10 @@ void evsel__delete(struct evsel *evsel) > { > evsel__exit(evsel); > free(evsel); > + > + /* just free it for the first evsel */ > + hashmap__free(perf_missing_features.pmu); > + perf_missing_features.pmu = NULL;
should this just remove evsel from perf_missing_features.pmu?
I'm not sure when we should actually release this.. what's your rationale for releasing it in here?
> } > > void evsel__compute_deltas(struct evsel *evsel, int cpu, int thread, > @@ -1791,6 +1795,23 @@ static int __evsel__prepare_open(struct evsel *evsel, struct perf_cpu_map *cpus, > return 0; > } > > +#define PMU_HASH_BITS 4 > + > +static size_t pmu_hash(const void *key, void *ctx __maybe_unused) > +{ > + const struct evsel *evsel = key; > + > + return hash_bits(evsel->core.attr.type, PMU_HASH_BITS); > +} > + > +static bool pmu_equal(const void *key1, const void *key2, void *ctx __maybe_unused) > +{ > + const struct evsel *a = key1; > + const struct evsel *b = key2; > + > + return a->core.attr.type == b->core.attr.type; > +} > + > static void evsel__disable_missing_features(struct evsel *evsel) > { > if (perf_missing_features.weight_struct) { > @@ -1807,8 +1828,13 @@ 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) > - evsel->core.attr.exclude_guest = evsel->core.attr.exclude_host = 0; > + if (perf_missing_features.exclude_guest) { > + /* we only have EXCLUDE_GUEST bit, let's skip checking */ > + if (hashmap__find(perf_missing_features.pmu, evsel, NULL)) { > + evsel->core.attr.exclude_guest = 0; > + evsel->core.attr.exclude_host = 0; > + } > + } > if (perf_missing_features.lbr_flags) > evsel->core.attr.branch_sample_type &= ~(PERF_SAMPLE_BRANCH_NO_FLAGS | > PERF_SAMPLE_BRANCH_NO_CYCLES); > @@ -1840,6 +1866,9 @@ int evsel__prepare_open(struct evsel *evsel, struct perf_cpu_map *cpus, > > bool evsel__detect_missing_features(struct evsel *evsel) > { > + if (perf_missing_features.pmu == NULL) > + perf_missing_features.pmu = hashmap__new(pmu_hash, pmu_equal, NULL);
missing allocation fail check
thanks, jirka
> + > /* > * Must probe features in the order they were added to the > * perf_event_attr interface. > @@ -1900,10 +1929,16 @@ 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)) { > - perf_missing_features.exclude_guest = true; > - pr_debug2_peo("switching off exclude_guest, exclude_host\n"); > + } else if ((evsel->core.attr.exclude_guest || evsel->core.attr.exclude_host) && > + !hashmap__find(perf_missing_features.pmu, evsel, NULL)) { > + uintptr_t pmu_features = PERF_MISSING_PMU_EXCLUDE_GUEST; > + > + hashmap__add(perf_missing_features.pmu, evsel, (void *)pmu_features); > + > + 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; > diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h > index 1f7edfa8568a..11b5ece19f0e 100644 > --- a/tools/perf/util/evsel.h > +++ b/tools/perf/util/evsel.h > @@ -172,6 +172,13 @@ struct perf_missing_features { > bool data_page_size; > bool code_page_size; > bool weight_struct; > + > + /* contains enum perf_missing_pmu_features below */ > + struct hashmap *pmu; > +}; > + > +enum perf_missing_pmu_features { > + PERF_MISSING_PMU_EXCLUDE_GUEST = 1UL << 0, > }; > > extern struct perf_missing_features perf_missing_features; > -- > 2.33.0.1079.g6e70778dc9-goog >
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