Date:   Fri, 10 Dec 2021 09:04:25 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Jiri Olsa <jolsa@redhat.com>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Michael Petlan <mpetlan@redhat.com>,
        Ian Rogers <irogers@google.com>,
        linux-perf-users@vger.kernel.org,
        "Frank Ch. Eigler" <fche@redhat.com>
Subject: Re: [RFC] perf record: Disable debuginfod by default
Message-ID: <20211210080425.GO16608@worktop.programming.kicks-ass.net>
References: <20211209200425.303561-1-jolsa@kernel.org>
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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.