Messages in this thread | | | Date | Sun, 17 Oct 2021 23:06:57 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH] perf evsel: Fix missing exclude_{host,guest} setting |
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On Sun, Oct 17, 2021 at 06:03:21PM -0300, Arnaldo Carvalho de Melo wrote: > > > On October 17, 2021 4:05:46 PM GMT-03:00, Jiri Olsa <jolsa@redhat.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@google.com> > >> Signed-off-by: Namhyung Kim <namhyung@kernel.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
ugh right... 'instead of &pmu' ;-)
thanks, jirka
> > > > >> + > >> + 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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