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

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Date:   Fri, 10 Dec 2021 13:24:40 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Ian Rogers <irogers@...gle.com>,
        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 09:04:25AM +0100, Peter Zijlstra wrote:
> On Thu, Dec 09, 2021 at 09:04:25PM +0100, Jiri Olsa 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 ;-)
> > 
> > thanks,
> > jirka
> > 
> > 
> > ---
> > Fedora 35 sets by default DEBUGINFOD_URLS, which might lead
> > to unexpected stalls in perf record exit path, when we try
> > to cache profiled binaries.
> > 
> >   # DEBUGINFOD_PROGRESS=1 ./perf record -a
> >   ^C[ perf record: Woken up 1 times to write data ]
> >   Downloading from https://debuginfod.fedoraproject.org/ 447069
> >   Downloading from https://debuginfod.fedoraproject.org/ 1502175
> >   Downloading \^Z
> > 
> > Disabling DEBUGINFOD_URLS by default in perf record and adding
> > debuginfod option and .perfconfig variable support to enable id.
> > 
> >   Default without debuginfo processing:
> >   # perf record -a
> > 
> >   Using system debuginfod setup:
> >   # perf record -a --debuginfod
> > 
> >   Using custom debuginfd url:
> >   # perf record -a --debuginfod='https://evenbetterdebuginfodserver.krava'
> > 
> > Adding single perf_debuginfod_setup function and using
> > it also in perf buildid-cache command.
> 
> I'm still running with --no-buildid --no-buildid-cache or something like
> that by default. As long as that remains working I'm good.

you're good ;-) that will bypass the problem completely

jirka