linux-kernel - Re: [PATCH 2/3] perf lock: Add -m/--map-length option

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Date:   Tue, 2 Aug 2022 11:05:09 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Song Liu <songliubraving@...com>,
        Blake Jones <blakejones@...gle.com>
Subject: Re: [PATCH 2/3] perf lock: Add -m/--map-length option

On Tue, Aug 2, 2022 at 10:43 AM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> Em Tue, Aug 02, 2022 at 12:35:10AM -0700, Namhyung Kim escreveu:
> > The -m/--map-length option is to control number of max entries in the
> > perf lock contention BPF maps.
> >
> > Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> > ---
> >  tools/perf/Documentation/perf-lock.txt |  4 ++++
> >  tools/perf/builtin-lock.c              | 23 ++++++++++++++++++++++-
> >  tools/perf/util/bpf_lock_contention.c  |  3 +++
> >  tools/perf/util/lock-contention.h      |  1 +
> >  4 files changed, 30 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/Documentation/perf-lock.txt b/tools/perf/Documentation/perf-lock.txt
> > index 7949d2e6891b..2101644785e0 100644
> > --- a/tools/perf/Documentation/perf-lock.txt
> > +++ b/tools/perf/Documentation/perf-lock.txt
> > @@ -145,6 +145,10 @@ CONTENTION OPTIONS
> >  --tid=::
> >          Record events on existing thread ID (comma separated list).
> >
> > +-m::
> > +--map-length::
> > +     Maximum number of BPF map entries (default: 10240).
>
> --map-nr-entries?
>
> I think we use this jargon "nr-entries" for arrays, lists, etc, better
> try to stick to it.

Makes sense, will change.

>
> Also what do you think about not using single letter options for things
> that are not that used?
>
> The map size has a default, one that seems generous, so changing it
> should be something uncommon, and then, if it becomes common that more
> entries are needed by default, we can change the default in the tool.

Fair enough, I'll remove the single letter option.

Thanks,
Namhyung