Messages in this thread Patch in this message | | | From | Namhyung Kim <> | Subject | [PATCH] perf evsel: Fix missing exclude_{host,guest} setting | Date | Fri, 15 Oct 2021 22:12:53 -0700 |
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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.
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; + + 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 }; + 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; }; extern struct perf_missing_features perf_missing_features; -- 2.33.0.1079.g6e70778dc9-goog
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