linux-kernel - Re: [PATCH 0/6] perf tools: Add wallclock time conversion support

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Message-ID: <a59b833f-bcb7-3d1b-6e0c-8758b47b93a3@gmail.com>
Date:   Thu, 30 Jul 2020 19:21:54 -0600
From:   David Ahern <dsahern@...il.com>
To:     peterz@...radead.org, Jiri Olsa <jolsa@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Ian Rogers <irogers@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Geneviève Bastien <gbastien@...satic.net>,
        Wang Nan <wangnan0@...wei.com>,
        Jeremie Galarneau <jgalar@...icios.com>
Subject: Re: [PATCH 0/6] perf tools: Add wallclock time conversion support

On 7/30/20 4:14 PM, peterz@...radead.org wrote:
> On Thu, Jul 30, 2020 at 11:39:44PM +0200, Jiri Olsa wrote:
> 
>> The patchset is adding the ability to display TOD/wallclock timestamp
>> in 'perf script' output and in 'perf data convert --to-ctf' subcommand,
>> so the converted CTF data contain TOD/wallclock timestamps.
> 
> But why? Wallclock is a horrible piece of crap. Why would you want to do
> this?
> 

Same reason I brought this up 9+ years ago: userspace lives on
time-of-day, and troubleshooting is based on correlating timestamps from
multiple sources. To correlate a perf event to syslog or an application
log, we need time-of-day.