Messages in this thread Patch in this message | | | Date | Sat, 6 Nov 2021 16:09:49 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v4] perf evsel: Fix missing exclude_{host,guest} setting |
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Em Fri, Nov 05, 2021 at 01:58:47PM -0700, Namhyung Kim escreveu: > 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.
⬢[acme@toolbox perf]$ perf test python 19: 'import perf' in python : FAILED! ⬢[acme@toolbox perf]$ perf test -v python Couldn't bump rlimit(MEMLOCK), failures may take place when creating BPF maps, etc 19: 'import perf' in python : --- start --- test child forked, pid 11602 python usage test: "echo "import sys ; sys.path.append('/tmp/build/perf/python'); import perf" | '/usr/bin/python3' " Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: /tmp/build/perf/python/perf.cpython-39-x86_64-linux-gnu.so: undefined symbol: evsel__find_pmu test child finished with -1 ---- end ---- 'import perf' in python: FAILED! ⬢[acme@toolbox perf]$
Trying to fix this now. please do a 'perf test' before submitting patches.
- Arnaldo
> 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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- Arnaldo
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