linux-kernel - Re: [PATCH v4 1/5] perf stat: Add AGGR_PCIE

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Message-ID: <CAM9d7ci6EmCLDxb3mYobsgndy5oA0vbEKztMuQUHE_O=KDSTeQ@mail.gmail.com>
Date:   Wed, 10 Feb 2021 19:02:06 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Alexander Antonov <alexander.antonov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Ian Rogers <irogers@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v4 1/5] perf stat: Add AGGR_PCIE_PORT mode

On Mon, Feb 8, 2021 at 8:31 PM Alexander Antonov
<alexander.antonov@...ux.intel.com> wrote:
>
> On 2/4/2021 3:07 PM, Namhyung Kim wrote:
> > Hello,
> >
> > On Wed, Feb 3, 2021 at 10:58 PM Alexander Antonov
> > <alexander.antonov@...ux.intel.com> wrote:
> >> Adding AGGR_PCIE_PORT mode to be able to distinguish aggr_mode
> >> for root ports in following patches.
> > I'm not sure adding the AGGR_PCIE_PORT is the right way.
> > In my understanding, the aggr mode is to specify how we aggregate
> > counter values of a single event from different cpus.  But this seems
> > to aggregate counter values from different events.  Also the new
> > mode is basically the same as AGGR_GLOBAL.
> >
> > As you will add stat_config.iostat_run to distinguish the iostat
> > command, probably we just want to use the global aggr mode
> > (and it's the default!) and get rid of the AGGR_PCIE_PORT.
> >
> > Thoughts?
> >
> > Thanks,
> > Namhyung
> Hello Namhyung,
>
> Actually, you are right. We aggregate counter values from different
> events of a
> single IIO stack (PCIe root port) to calculate metrics for this IO stack.
> But the reason is to prevent using of '-e' and '-M' options in 'iostat' mode
> because it can be a reason for the mess in the output that can confuse
> users.
>
> There is an idea to use your suggestion for this part:
>
> status = iostat_prepare(...);
> if (status < 0)
>          goto out;
> if (status == IOSTAT_LIST)
>          iostat_list(...);
> else
>          ...
>
> So, we can check if evlist is empty inside iostat_prepare(). If not, print
> a warning, for example, "The -e and -M options are not supported. All chosen
> events/metrics will be dropped". Then we can free of evlist by using
> evlist__delete(), create new one by using evlist__new() and fill the evlist.
>
> In this case the body of iostat_prepare() function would be:
>
> iostat_prepare()
> {
>      If (!is_evlist_empty) {
>          pr_warning();
>          evlist__delete();
>          evlist__new()
>      }
>
>      iostat_event_group();
> }
>
> It will allow to get rid of the AGGR_PCIE_PORT.
> What do you think?

LGTM :)

Thanks,
Namhyung