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Message-ID: <CAM9d7cjCV8qb2M9CW+NV2KpCwBTBAMWyE36yAL5SMFQ4wfxJfQ@mail.gmail.com>
Date: Thu, 10 Sep 2020 14:51:13 +0900
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>, Kajol Jain <kjain@...ux.ibm.com>,
Kan Liang <kan.liang@...ux.intel.com>,
Jin Yao <yao.jin@...ux.intel.com>,
Thomas Richter <tmricht@...ux.ibm.com>,
linux-kernel <linux-kernel@...r.kernel.org>,
Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v2 3/3] perf metricgroup: Fix uncore metric expressions
On Thu, Sep 10, 2020 at 12:26 PM Ian Rogers <irogers@...gle.com> wrote:
>
> A metric like DRAM_BW_Use has on SkylakeX events uncore_imc/cas_count_read/
> and uncore_imc/case_count_write/. These events open 6 events per socket
> with pmu names of uncore_imc_[0-5]. The current metric setup code in
> find_evsel_group assumes one ID will map to 1 event to be recorded in
> metric_events. For events with multiple matches, the first event is
> recorded in metric_events (avoiding matching >1 event with the same
> name) and the evlist_used updated so that duplicate events aren't
> removed when the evlist has unused events removed.
>
> Before this change:
> $ /tmp/perf/perf stat -M DRAM_BW_Use -a -- sleep 1
>
> Performance counter stats for 'system wide':
>
> 41.14 MiB uncore_imc/cas_count_read/
> 1,002,614,251 ns duration_time
>
> 1.002614251 seconds time elapsed
>
> After this change:
> $ /tmp/perf/perf stat -M DRAM_BW_Use -a -- sleep 1
>
> Performance counter stats for 'system wide':
>
> 157.47 MiB uncore_imc/cas_count_read/ # 0.00 DRAM_BW_Use
> 126.97 MiB uncore_imc/cas_count_write/
> 1,003,019,728 ns duration_time
>
> v2. avoids iterating over the whole evlist as suggested by
> namhyung@...nel.org. It also fixes the metric_leader computation
> that was broken in the same commits.
>
> Erroneous duplication introduced in:
> commit 2440689d62e9 ("perf metricgroup: Remove duped metric group events").
>
> Fixes: ded80bda8bc9 ("perf expr: Migrate expr ids table to a hashmap").
> Reported-by: Jin Yao <yao.jin@...ux.intel.com>
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
> tools/perf/util/metricgroup.c | 45 ++++++++++++++++++++++++++++++++---
> 1 file changed, 42 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> index 662f4e8777d5..79080de9217d 100644
> --- a/tools/perf/util/metricgroup.c
> +++ b/tools/perf/util/metricgroup.c
> @@ -206,6 +206,18 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
> sizeof(struct evsel *) * idnum);
> current_leader = ev->leader;
> }
> + /*
> + * Check for duplicate events with the same name. For example,
> + * uncore_imc/cas_count_read/ will turn into 6 events per socket
> + * on skylakex. Only the first such event is placed in
> + * metric_events.
> + */
> + for (i = 0; i < matched_events; i++) {
> + if (!strcmp(metric_events[i]->name, ev->name))
> + break;
> + }
> + if (i != matched_events)
> + continue;
We have the same logic in the below. Maybe it'd better to factor out..
> if (hashmap__find(&pctx->ids, ev->name, (void **)&val_ptr)) {
> if (has_constraint) {
> /*
> @@ -245,9 +257,36 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
> metric_events[idnum] = NULL;
>
> for (i = 0; i < idnum; i++) {
> - ev = metric_events[i];
> - ev->metric_leader = ev;
> - set_bit(ev->idx, evlist_used);
> + /* Don't free used events. */
> + set_bit(metric_events[i]->idx, evlist_used);
> + /*
> + * The metric leader points to the identically named event in
> + * metric_events.
> + */
> + metric_events[i]->metric_leader = metric_events[i];
> + /*
> + * Mark two events with identical names in the same group (or
> + * globally) as being in use as uncore events may be duplicated
> + * for each pmu. Set the metric leader to be the event that
> + * appears in metric_events.
> + */
I thought this again, and it's not guaranteed that the metric leader is
a group leader so below won't work IMHO. Instead we should iterate
evlist always, but started from the metric leader with the
evlist__for_each_entry_continue.
Thanks
Namhyung
> + if (!has_constraint) {
> + for_each_group_evsel(ev, metric_events[i]->leader) {
> + if (ev != metric_events[i] &&
> + !strcmp(metric_events[i]->name, ev->name)) {
> + set_bit(ev->idx, evlist_used);
> + ev->metric_leader = metric_events[i];
> + }
> + }
> + } else {
> + evlist__for_each_entry(perf_evlist, ev) {
> + if (ev != metric_events[i] &&
> + !strcmp(metric_events[i]->name, ev->name)) {
> + set_bit(ev->idx, evlist_used);
> + ev->metric_leader = metric_events[i];
> + }
> + }
> + }
> }
>
> return metric_events[0];
> --
> 2.28.0.526.ge36021eeef-goog
>
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