perf stat: Use group read for event groups
Make perf stat use group read if there are groups defined. The group read will get the values for all member of groups within a single syscall instead of calling read syscall for every event. We can see considerable less amount of kernel cycles spent on single group read, than reading each event separately, like for following perf stat command: # perf stat -e {cycles,instructions} -I 10 -a sleep 1 Monitored with "perf stat -r 5 -e '{cycles:u,cycles:k}'" Before: 24,325,676 cycles:u 297,040,775 cycles:k 1.038554134 seconds time elapsed After: 25,034,418 cycles:u 158,256,395 cycles:k 1.036864497 seconds time elapsed The perf_evsel__open fallback changes contributed by Andi Kleen. Signed-off-by: Jiri Olsa <jolsa@kernel.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: David Ahern <dsahern@gmail.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20170726120206.9099-4-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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@ -213,10 +213,20 @@ static void perf_stat__reset_stats(void)
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static int create_perf_stat_counter(struct perf_evsel *evsel)
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{
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struct perf_event_attr *attr = &evsel->attr;
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struct perf_evsel *leader = evsel->leader;
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if (stat_config.scale)
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if (stat_config.scale) {
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attr->read_format = PERF_FORMAT_TOTAL_TIME_ENABLED |
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PERF_FORMAT_TOTAL_TIME_RUNNING;
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}
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/*
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* The event is part of non trivial group, let's enable
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* the group read (for leader) and ID retrieval for all
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* members.
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*/
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if (leader->nr_members > 1)
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attr->read_format |= PERF_FORMAT_ID|PERF_FORMAT_GROUP;
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attr->inherit = !no_inherit;
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@ -333,13 +343,21 @@ static int read_counter(struct perf_evsel *counter)
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struct perf_counts_values *count;
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count = perf_counts(counter->counts, cpu, thread);
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if (perf_evsel__read(counter, cpu, thread, count)) {
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/*
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* The leader's group read loads data into its group members
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* (via perf_evsel__read_counter) and sets threir count->loaded.
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*/
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if (!count->loaded &&
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perf_evsel__read_counter(counter, cpu, thread)) {
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counter->counts->scaled = -1;
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perf_counts(counter->counts, cpu, thread)->ena = 0;
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perf_counts(counter->counts, cpu, thread)->run = 0;
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return -1;
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}
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count->loaded = false;
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if (STAT_RECORD) {
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if (perf_evsel__write_stat_event(counter, cpu, thread, count)) {
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pr_err("failed to write stat event\n");
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@ -559,6 +577,11 @@ static int store_counter_ids(struct perf_evsel *counter)
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return __store_counter_ids(counter, cpus, threads);
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}
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static bool perf_evsel__should_store_id(struct perf_evsel *counter)
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{
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return STAT_RECORD || counter->attr.read_format & PERF_FORMAT_ID;
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}
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static int __run_perf_stat(int argc, const char **argv)
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{
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int interval = stat_config.interval;
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@ -631,7 +654,8 @@ try_again:
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if (l > unit_width)
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unit_width = l;
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if (STAT_RECORD && store_counter_ids(counter))
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if (perf_evsel__should_store_id(counter) &&
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store_counter_ids(counter))
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return -1;
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}
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@ -12,6 +12,7 @@ struct perf_counts_values {
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};
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u64 values[3];
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};
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bool loaded;
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};
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struct perf_counts {
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@ -49,6 +49,7 @@ static struct {
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bool clockid_wrong;
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bool lbr_flags;
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bool write_backward;
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bool group_read;
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} perf_missing_features;
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static clockid_t clockid;
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@ -1321,6 +1322,7 @@ perf_evsel__set_count(struct perf_evsel *counter, int cpu, int thread,
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count->val = val;
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count->ena = ena;
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count->run = run;
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count->loaded = true;
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}
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static int
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@ -1677,6 +1679,8 @@ fallback_missing_features:
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if (perf_missing_features.lbr_flags)
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evsel->attr.branch_sample_type &= ~(PERF_SAMPLE_BRANCH_NO_FLAGS |
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PERF_SAMPLE_BRANCH_NO_CYCLES);
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if (perf_missing_features.group_read && evsel->attr.inherit)
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evsel->attr.read_format &= ~(PERF_FORMAT_GROUP|PERF_FORMAT_ID);
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retry_sample_id:
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if (perf_missing_features.sample_id_all)
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evsel->attr.sample_id_all = 0;
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@ -1832,6 +1836,12 @@ try_fallback:
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perf_missing_features.lbr_flags = true;
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pr_debug2("switching off branch sample type no (cycles/flags)\n");
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goto fallback_missing_features;
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} else if (!perf_missing_features.group_read &&
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evsel->attr.inherit &&
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(evsel->attr.read_format & PERF_FORMAT_GROUP)) {
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perf_missing_features.group_read = true;
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pr_debug2("switching off group read\n");
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goto fallback_missing_features;
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}
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out_close:
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do {
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