linux-kernel - Re: [RFC] perf record: Disable debuginfod by default

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Message-ID: <CAM9d7cit-GKyDcVp435np7WSe_KW-+NYD7rHSC10EEoW1EpTSA@mail.gmail.com>
Date:   Fri, 10 Dec 2021 10:41:49 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Ian Rogers <irogers@...gle.com>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        "Frank Ch. Eigler" <fche@...hat.com>
Subject: Re: [RFC] perf record: Disable debuginfod by default

On Fri, Dec 10, 2021 at 4:23 AM Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Thu, Dec 09, 2021 at 03:39:20PM -0800, Namhyung Kim wrote:
> > Hi Jiri,
> >
> > On Thu, Dec 9, 2021 at 12:04 PM Jiri Olsa <jolsa@...hat.com> wrote:
> > >
> > > hi,
> > > after migrating to fedora 35 I found perf record hanging on exit
> > > and it's because fedora 35 sets DEBUGINFOD_URLS that triggers
> > > debuginfod query which might take long time to process.
> > >
> > > I discussed this briefly with Frank and I'm sending the change
> > > to disable debuginfod by default in perf record.
> > >
> > > Frank had other idea we could discuss here to fork or just spawn
> > > "/usr/bin/debuginfod-find ...." into background after perf record.
> > >
> > > Perhaps there are other ways as well, hence this is RFC ;-)
> >
> > I thought the debuginfod was for perf report, not record.
> > Maybe I'm missing something but how about moving it to
> > report?  We can talk to debuginfod after checking the local
> > build-id cache and binary on the system.
>
> at the end of the perf record we populate buildid cache
> with profiled binaries for the current perf.data
>
> **IF** there's DEBUGINFOD_URLS defined, that code will
> also ask debuginfod for binaries it could not find on
> the system

Yeah, I know what you're doing.  But I guess debuginfod
contains binaries for the distro and they'd be available for
a while.  Then I think we don't need to do it at perf record.

Thanks,
Namhyung