Re: [PATCH 2/3] perf metricgroup: Fix uncore metric expressions

[Namhyung Kim]

Hi Ian,

On Wed, Sep 9, 2020 at 5:02 PM Ian Rogers <irogers@xxxxxxxxxx> 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

Hmm.. I guess the 0.00 result is incorrect, no?


>             126.97 MiB  uncore_imc/cas_count_write/
>      1,003,019,728 ns   duration_time
>
> 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@xxxxxxxxxxxxxxx>
> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> ---
[SNIP]
> @@ -248,6 +260,16 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
>                 ev = metric_events[i];
>                 ev->metric_leader = ev;
>                 set_bit(ev->idx, evlist_used);
> +               /*
> +                * Mark two events with identical names in the same group as
> +                * being in use as uncore events may be duplicated for each pmu.
> +                */
> +               evlist__for_each_entry(perf_evlist, ev) {
> +                       if (metric_events[i]->leader == ev->leader &&
> +                           !strcmp(metric_events[i]->name, ev->name)) {
> +                               set_bit(ev->idx, evlist_used);

I'm not sure whether they are grouped together.
But if so, you can use for_each_group_member(ev, leader).

Thanks
Namhyung


> +                       }
> +               }
>         }
>
>         return metric_events[0];
> --
> 2.28.0.526.ge36021eeef-goog
>