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Date: Sun, 17 Oct 2021 18:03:21 -0300 From: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com> To: Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org> CC: Arnaldo Carvalho de Melo <acme@...nel.org>, Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>, LKML <linux-kernel@...r.kernel.org>, Andi Kleen <ak@...ux.intel.com>, Ian Rogers <irogers@...gle.com>, Stephane Eranian <eranian@...gle.com> Subject: Re: [PATCH] perf evsel: Fix missing exclude_{host,guest} setting On October 17, 2021 4:05:46 PM GMT-03:00, Jiri Olsa <jolsa@...hat.com> wrote: >On Fri, Oct 15, 2021 at 10:12:53PM -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@...gle.com> >> Signed-off-by: Namhyung Kim <namhyung@...nel.org> >> --- >> tools/perf/util/evsel.c | 47 +++++++++++++++++++++++++++++++++++------ >> tools/perf/util/evsel.h | 6 ++++++ >> 2 files changed, 47 insertions(+), 6 deletions(-) >> >> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c >> index dbfeceb2546c..437a28e769fe 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; >> } >> >> 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 +1828,14 @@ 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) { >> + void *pmu; > >could you just pass NULL in here instead of NULL? ENOPARSE > >> + >> + if (hashmap__find(perf_missing_features.pmu, evsel, &pmu)) { >> + 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 +1867,9 @@ 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); >> + >> /* >> * Must probe features in the order they were added to the >> * perf_event_attr interface. >> @@ -1900,10 +1930,15 @@ 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)) { >> + struct perf_missing_pmu_features pmu_features = { true }; > >missing new line after declaration > >> + hashmap__add(perf_missing_features.pmu, evsel, &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..8dd11c8e022d 100644 >> --- a/tools/perf/util/evsel.h >> +++ b/tools/perf/util/evsel.h >> @@ -172,6 +172,12 @@ struct perf_missing_features { >> bool data_page_size; >> bool code_page_size; >> bool weight_struct; >> + >> + struct hashmap *pmu; >> +}; >> + >> +struct perf_missing_pmu_features { >> + bool exclude_guest; >> }; > >hum, is this really needed? I think you could just pass '1' as value, >because you care only if the item is hashed, right? > >in any case the value is the current stack address of the > struct perf_missing_pmu_features pmu_features = { true }; > >so it might as well be just '1' ... I was confused at the beggining >and looked for the reason of this struct ;-) > >we do that already in util/stat.c > >jirka > >> >> extern struct perf_missing_features perf_missing_features; >> -- >> 2.33.0.1079.g6e70778dc9-goog >> >
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