linux-kernel - Re: [RFC PATCH v6 4/5] perf stat: Add retire latency print functions to print out at the very end of print out

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Date: Mon, 1 Apr 2024 14:15:16 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: "Wang, Weilin" <weilin.wang@...el.com>
Cc: Ian Rogers <irogers@...gle.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	"Hunter, Adrian" <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	"linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Taylor, Perry" <perry.taylor@...el.com>, 
	"Alt, Samantha" <samantha.alt@...el.com>, "Biggers, Caleb" <caleb.biggers@...el.com>
Subject: Re: [RFC PATCH v6 4/5] perf stat: Add retire latency print functions
 to print out at the very end of print out

On Mon, Apr 1, 2024 at 2:08 PM Wang, Weilin <weilin.wang@...el.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Namhyung Kim <namhyung@...nel.org>
> > Sent: Monday, April 1, 2024 2:04 PM
> > To: Wang, Weilin <weilin.wang@...el.com>
> > Cc: Ian Rogers <irogers@...gle.com>; Arnaldo Carvalho de Melo
> > <acme@...nel.org>; Peter Zijlstra <peterz@...radead.org>; Ingo Molnar
> > <mingo@...hat.com>; Alexander Shishkin
> > <alexander.shishkin@...ux.intel.com>; Jiri Olsa <jolsa@...nel.org>; Hunter,
> > Adrian <adrian.hunter@...el.com>; Kan Liang <kan.liang@...ux.intel.com>;
> > linux-perf-users@...r.kernel.org; linux-kernel@...r.kernel.org; Taylor, Perry
> > <perry.taylor@...el.com>; Alt, Samantha <samantha.alt@...el.com>; Biggers,
> > Caleb <caleb.biggers@...el.com>
> > Subject: Re: [RFC PATCH v6 4/5] perf stat: Add retire latency print functions to
> > print out at the very end of print out
> >
> > On Fri, Mar 29, 2024 at 12:12 PM <weilin.wang@...el.com> wrote:
> > >
> > > From: Weilin Wang <weilin.wang@...el.com>
> > >
> > > Add print out functions so that users could read retire latency values.
> > >
> > > Example output:
> > > In this simple example, there is no MEM_INST_RETIRED.STLB_HIT_STORES
> > sample.
> > > Therefore, the MEM_INST_RETIRED.STLB_HIT_STORES:p retire_latency
> > value, count
> > > and sum are all 0.
> > >
> > >  Performance counter stats for 'system wide':
> > >
> > >        181,047,168      cpu_core/TOPDOWN.SLOTS/          #      0.6 %
> > tma_dtlb_store
> > >          3,195,608      cpu_core/topdown-retiring/
> > >         40,156,649      cpu_core/topdown-mem-bound/
> > >          3,550,925      cpu_core/topdown-bad-spec/
> > >        117,571,818      cpu_core/topdown-fe-bound/
> > >         57,118,087      cpu_core/topdown-be-bound/
> > >             69,179      cpu_core/EXE_ACTIVITY.BOUND_ON_STORES/
> > >              4,582      cpu_core/MEM_INST_RETIRED.STLB_HIT_STORES/
> > >         30,183,104      cpu_core/CPU_CLK_UNHALTED.DISTRIBUTED/
> > >         30,556,790      cpu_core/CPU_CLK_UNHALTED.THREAD/
> > >            168,486      cpu_core/DTLB_STORE_MISSES.WALK_ACTIVE/
> > >               0.00 MEM_INST_RETIRED.STLB_HIT_STORES:p       0        0
> >
> > The output is not aligned and I think it's hard to read.
> > I think it should print the result like this:
> >
> >     <sum>  <event-name>  # <val>  average retired latency
>
> Since we would like to use the average retire latency, I would think put average
> at the beginning would be more consistent. So in format like:
> <val> <event-name> <sum> <count> or <val> <event-name> <count> <sum> ?

But it's not consistent with others.  When I see the perf stat
output, I'd expect it shows the total count.  And the average
latency is a derived value so I think it can be treated as a metric.

Thanks,
Namhyung