linux-kernel - Re: [PATCH v2] perf/core: Add a new read format to get a number of lost samples

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Message-ID: <CAM9d7cg_=EFQNVvEWsmNiQ_jjjiRSXjc=uH=4uQzuVbVNzuLDw@mail.gmail.com>
Date:   Wed, 22 Sep 2021 12:34:20 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH v2] perf/core: Add a new read format to get a number of
 lost samples

Hi Peter,

On Fri, Sep 10, 2021 at 3:40 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> On Fri, Sep 10, 2021 at 2:42 PM Jiri Olsa <jolsa@...hat.com> wrote:
> >
> > On Wed, Sep 08, 2021 at 10:24:20AM -0700, Namhyung Kim wrote:
> > > Sometimes we want to know an accurate number of samples even if it's
> > > lost.  Currenlty PERF_RECORD_LOST is generated for a ring-buffer which
> > > might be shared with other events.  So it's hard to know per-event
> > > lost count.
> > >
> > > Add event->lost_samples field and PERF_FORMAT_LOST to retrieve it from
> > > userspace.
> >
> > hi,
> > looks good.. will there be some tools/perf change using this?
>
> Sure, I'll work on the userspace part after this is merged.
> I'm thinking about adding LOST_SAMPLES records at the end
> of the data section as if they came from the kernel.

Can I get your feedback?

Thanks,
Namhyung