Re: [PATCH v1] perf stat: Fix uncore aggregation number

[Namhyung Kim <namhyung@kernel.org>]

On Mon, Jun 23, 2025 at 11:17:20AM -0700, Ian Rogers wrote:
> On Fri, Jun 20, 2025 at 3:12 PM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > Hi CT,
> >
> > On Thu, Jun 12, 2025 at 03:55:59PM -0700, Chun-Tse Shao wrote:
> > > Hi Ian, I actually renamed it to `aggr_nr` in v2 patch so it should be
> > > better aligned to json mode, which is using `aggregate-nunber`. But
> > > anyway I think any name other than `cpus` is better.
> > > v2 patch: lore.kernel.org/20250612225324.3315450-1-ctshao@google.com
> >
> > I think "aggregation-count" is a better name, maybe abbreviated to
> > "ag_cnt".  Can we rename the JSON as well?  I'm not sure if it's
> > documented somewhere.
> 
> Fwiw, I still think "counters" is a clearer, more intention revealing
> definition than "aggregation count" or "aggregation number". The term
> counter appears in the perf-stat and perf_event_open man page. In the
> perf-stat man page we have a pattern of:
> 
>        --per-XXX
>            Aggregate counts per XXX for system-wide mode measurements. This is a
>            useful mode to .... To enable this mode, use --per-XXX
>            in addition to -a. (system-wide). The output includes the ...
>           This is useful to gauge the amount of aggregation.
> 
> It seems that the aggregated value of the counters could be confused
> for being an "aggregation count" or "aggregation number" given the man
> page definition. I think "counters" to some extent avoids this, we
> giving the number of counters aggregated. The perf-stat man page could
> certainly be clearer :-)

I'm fine with "counters" (and "ctrs").

Thanks,
Namhyung

> > >
> > > On Wed, Jun 11, 2025 at 10:12 PM Ian Rogers <irogers@google.com> wrote:
> > > >
> > > > On Wed, Jun 11, 2025 at 8:18 PM Chun-Tse Shao <ctshao@google.com> wrote:
> > > > >
> > > > > Thanks for your test, Ian!
> > > > >
> > > > > I wonder if `nr_pmus` makes sense, since the column would be shared
> > > > > with multiple different pmus. WDYT?
> > > >
> > > > So each PMU in sysfs has a cpumask that specifies which CPUs perf
> > > > should pass to perf_event_open. For example, on a two socket machine
> > > > the cpumask will typically have the first CPU of each socket. If the
> > > > cpumask (or cpus) file isn't present then the cpumask is implicitly
> > > > all online CPUs. Given that the aggregation number is the number of
> > > > CPUs in the cpumask multiplied by the number of PMUs, I think the most
> > > > neutral name is probably "counters" possibly shortened down to "ctrs".
> > > > I suspect others have better suggestions :-)
> > > >
> > > > Thanks,
> > > > Ian
> > > >
> > > > > -CT
> > > > >
> > > > > On Wed, Jun 11, 2025 at 5:16 PM Ian Rogers <irogers@google.com> wrote:
> > > > > >
> > > > > > On Wed, Jun 11, 2025 at 4:36 PM Chun-Tse Shao <ctshao@google.com> wrote:
> > > > > > >
> > > > > > > Follow up:
> > > > > > > lore.kernel.org/CAP-5=fVDF4-qYL1Lm7efgiHk7X=_nw_nEFMBZFMcsnOOJgX4Kg@mail.gmail.com/
> > > > > > >
> > > > > > > The patch adds unit aggregation during evsel merge the aggregated uncore
> > > > > > > counters.
> > > > > > >
> > > > > > > Tested on a 2-socket machine with SNC3, uncore_imc_[0-11] and
> > > > > > > cpumask="0,120"
> > > > > > > Before:
> > > > > > >   perf stat -e clockticks -I 1000 --per-socket
> > > > > > >   #           time socket cpus             counts unit events
> > > > > > >        1.001085024 S0        1         9615386315      clockticks
> > > > > > >        1.001085024 S1        1         9614287448      clockticks
> > > > > > >   perf stat -e clockticks -I 1000 --per-node
> > > > > > >   #           time node   cpus             counts unit events
> > > > > > >        1.001029867 N0        1         3205726984      clockticks
> > > > > > >        1.001029867 N1        1         3205444421      clockticks
> > > > > > >        1.001029867 N2        1         3205234018      clockticks
> > > > > > >        1.001029867 N3        1         3205224660      clockticks
> > > > > > >        1.001029867 N4        1         3205207213      clockticks
> > > > > > >        1.001029867 N5        1         3205528246      clockticks
> > > > > > > After:
> > > > > > >   perf stat -e clockticks -I 1000 --per-socket
> > > > > > >   #           time socket cpus             counts unit events
> > > > > >
> > > > > > I wonder if there is a better column heading than "cpus" given that
> > > > > > these are imc PMUs.
> > > > > >
> > > > > > >        1.001022937 S0       12         9621463177      clockticks
> > > > > > >        1.001022937 S1       12         9619804949      clockticks
> > > > > > >   perf stat -e clockticks -I 1000 --per-node
> > > > > > >   #           time node   cpus             counts unit events
> > > > > > >        1.001029867 N0        4         3206782080      clockticks
> > > > > > >        1.001029867 N1        4         3207025354      clockticks
> > > > > > >        1.001029867 N2        4         3207067946      clockticks
> > > > > > >        1.001029867 N3        4         3206871733      clockticks
> > > > > > >        1.001029867 N4        4         3206199005      clockticks
> > > > > > >        1.001029867 N5        4         3205525058      clockticks
> > > > > > >
> > > > > > > Suggested-by: Ian Rogers <irogers@google.com>
> > > > > > > Signed-off-by: Chun-Tse Shao <ctshao@google.com>
> > > > >
> > > > > Added Namhyung's ack from the previous email.
> > > > > Acked-by: Namhyung Kim <namhyung@kernel.org>
> > > > >
> > > > > >
> > > > > > Tested-by: Ian Rogers <irogers@google.com>
> > > > > >
> > > > > > Thanks,
> > > > > > Ian
> > > > > >
> > > > > > > ---
> > > > > > >  tools/perf/util/stat.c | 1 +
> > > > > > >  1 file changed, 1 insertion(+)
> > > > > > >
> > > > > > > diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
> > > > > > > index 355a7d5c8ab8..52266d773353 100644
> > > > > > > --- a/tools/perf/util/stat.c
> > > > > > > +++ b/tools/perf/util/stat.c
> > > > > > > @@ -527,6 +527,7 @@ static int evsel__merge_aggr_counters(struct evsel *evsel, struct evsel *alias)
> > > > > > >                 struct perf_counts_values *aggr_counts_b = &ps_b->aggr[i].counts;
> > > > > > >
> > > > > > >                 /* NB: don't increase aggr.nr for aliases */
> > > > > > > +               ps_a->aggr[i].nr += ps_b->aggr[i].nr;
> > > > > > >
> > > > > > >                 aggr_counts_a->val += aggr_counts_b->val;
> > > > > > >                 aggr_counts_a->ena += aggr_counts_b->ena;
> > > > > > > --
> > > > > > > 2.50.0.rc1.591.g9c95f17f64-goog
> > > > > > >