From: Milian Wolff <milian.wolff@kdab.com>
To: Bram Stolk <b.stolk@gmail.com>
Cc: linux-perf-users@vger.kernel.org, Arnaldo Carvalho <acme@kernel.org>
Subject: Re: Wildly different output sizes between subsequent perf record runs.
Date: Mon, 06 Nov 2017 13:06:56 +0100 [thread overview]
Message-ID: <5922369.x0IdO5xPIl@agathebauer> (raw)
In-Reply-To: <CABYXEkvrMhd9+P01k94AE97YHooDcs8Nxn4UfuvKfzzq88foVA@mail.gmail.com>
On Samstag, 4. November 2017 02:57:01 CET Bram Stolk wrote:
> If I do subsequent runs of 'perf record', both of which are identical,
> I sometimes get wildly different output sizes.
>
>
> https://gist.github.com/stolk/3666b2b4d4319764fdff4a2d4c619782
>
> The binary did the same amount of work, and took the same amount of
> time to execute.
> This is with using perf from Ubuntu LTS.
I think this is the same bug that I have raised before. See https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1479712.html and below.
Can you try to run your command with a constant period (`-c 3000000` or
similar), instead of using a dynamic period (i.e. `--freq`)? Does the issue go
away then? If yes, then it's the same issue that I described earlier, which
noone else from the perf team has acknowledged so far. I know multiple people
who are affected by this though...
--
Milian Wolff | milian.wolff@kdab.com | Senior Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts
next prev parent reply other threads:[~2017-11-06 12:07 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-04 1:57 Wildly different output sizes between subsequent perf record runs Bram Stolk
2017-11-06 12:06 ` Milian Wolff [this message]
2017-11-06 17:38 ` Bram Stolk
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