linux-kernel - Re: [PATCH v5 08/50] perf record: Be lazier in allocating lost samples buffer

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Message-ID: <CAM9d7chU1Jyurb6bmZOSmeuFky9eN+2Ty7kMrQxyUXN=r0FKvg@mail.gmail.com>
Date:   Sat, 2 Dec 2023 15:56:48 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Nick Terrell <terrelln@...com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        "Steinar H. Gunderson" <sesse@...gle.com>,
        Liam Howlett <liam.howlett@...cle.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Colin Ian King <colin.i.king@...il.com>,
        Dmitrii Dolgov <9erthalion6@...il.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        Ming Wang <wangming01@...ngson.cn>,
        James Clark <james.clark@....com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        Leo Yan <leo.yan@...aro.org>,
        Ravi Bangoria <ravi.bangoria@....com>,
        German Gomez <german.gomez@....com>,
        Changbin Du <changbin.du@...wei.com>,
        Paolo Bonzini <pbonzini@...hat.com>, Li Dong <lidong@...o.com>,
        Sandipan Das <sandipan.das@....com>,
        liuwenyu <liuwenyu7@...wei.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org,
        Guilherme Amadio <amadio@...too.org>
Subject: Re: [PATCH v5 08/50] perf record: Be lazier in allocating lost
 samples buffer

On Thu, Nov 30, 2023 at 10:29 AM Ian Rogers <irogers@...gle.com> wrote:
>
> On Wed, Nov 29, 2023 at 6:09 PM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > On Mon, Nov 27, 2023 at 2:09 PM Ian Rogers <irogers@...gle.com> wrote:
> > >
> > > Wait until a lost sample occurs to allocate the lost samples buffer,
> > > often the buffer isn't necessary. This saves a 64kb allocation and
> > > 5.3kb of peak memory consumption.
> > >
> > > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > > ---
> > >  tools/perf/builtin-record.c | 29 +++++++++++++++++++----------
> > >  1 file changed, 19 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > > index 9b4f3805ca92..b6c8c1371b39 100644
> > > --- a/tools/perf/builtin-record.c
> > > +++ b/tools/perf/builtin-record.c
> > > @@ -1924,21 +1924,13 @@ static void __record__save_lost_samples(struct record *rec, struct evsel *evsel,
> > >  static void record__read_lost_samples(struct record *rec)
> > >  {
> > >         struct perf_session *session = rec->session;
> > > -       struct perf_record_lost_samples *lost;
> > > +       struct perf_record_lost_samples *lost = NULL;
> > >         struct evsel *evsel;
> > >
> > >         /* there was an error during record__open */
> > >         if (session->evlist == NULL)
> > >                 return;
> > >
> > > -       lost = zalloc(PERF_SAMPLE_MAX_SIZE);
> >
> > To minimize the allocation size, this can be
> > sizeof(*lost) + session->machines.host.id_hdr_size
> > instead of PERF_SAMPLE_MAX_SIZE.
>
> Sounds good, should probably be a follow up. The current size is
> PERF_SAMPLE_MAX_SIZE.

Yep, I'm ok with having it as a follow-up.

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung