Messages in this thread Patch in this message | | | From | Namhyung Kim <> | Subject | [PATCH v4] perf evsel: Fix missing exclude_{host,guest} setting | Date | Fri, 5 Nov 2021 13:58:47 -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> Cc: Ravi Bangoria <ravi.bangoria@amd.com> Signed-off-by: Namhyung Kim <namhyung@kernel.org> --- v4 changes) * add pmu->missing_features.exclude_guest * bail out if evsel->exclude_GH is set
v3 changes) * check memory allocation failure * add more NULL check
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 | 27 ++++++++++++++++++++++----- tools/perf/util/evsel.h | 4 ++++ tools/perf/util/pmu.h | 4 ++++ 3 files changed, 30 insertions(+), 5 deletions(-)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index 2cfc2935d1d2..3cc1f8fcf15c 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -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)) { - 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) && + (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; diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h index 846c827934de..dcc87c2881b8 100644 --- a/tools/perf/util/evsel.h +++ b/tools/perf/util/evsel.h @@ -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 { diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h index 15bbec3a9959..541889fa9f9c 100644 --- a/tools/perf/util/pmu.h +++ b/tools/perf/util/pmu.h @@ -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; -- 2.34.0.rc0.344.g81b53c2807-goog
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