Messages in this thread | | | From | Namhyung Kim <> | Date | Sun, 17 Oct 2021 21:53:13 -0700 | Subject | Re: [PATCH] perf evsel: Fix missing exclude_{host,guest} setting |
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On Sun, Oct 17, 2021 at 2:07 PM Jiri Olsa <jolsa@redhat.com> wrote: > > 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' ;-)
Yes, we can pass NULL for the current code. Passing the pointer is just for future change. Maybe I thought too much.. :)
Anyway, I think it should pass the struct itself, not the pointer to the local variable. I'm not sure if it's possible to cast a struct literal to a pointer, will check and update in v2.
Thanks, Namhyung
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