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Message-Id: <20211026043351.56662-1-namhyung@kernel.org>
Date: Mon, 25 Oct 2021 21:33:51 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
Jiri Olsa <jolsa@...hat.com>
Cc: 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: [PATCH v2] perf evsel: Fix missing exclude_{host,guest} setting
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>
---
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;
}
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);
+
/*
* 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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