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

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Date:   Fri, 10 Dec 2021 13:23:32 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Namhyung Kim <namhyung@...nel.org>
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 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

> 
> Still, we can have perf buildid-cache to move it from the
> debuginfod to local cache.

yep, we have that already

jirka