From: Peter Zijlstra <peterz@infradead.org>
To: Denys Vlasenko <dvlasenk@redhat.com>
Cc: linux-kernel@vger.kernel.org,
Frederic Weisbecker <fweisbec@gmail.com>,
Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>,
Fernando Luis Vazquez Cao <fernando_b1@lab.ntt.co.jp>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Arjan van de Ven <arjan@linux.intel.com>,
Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH 3/4 v2] nohz: Fix idle/iowait counts going backwards
Date: Wed, 7 May 2014 16:23:21 +0200 [thread overview]
Message-ID: <20140507142321.GA2844@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <1399470094-8070-3-git-send-email-dvlasenk@redhat.com>
On Wed, May 07, 2014 at 03:41:33PM +0200, Denys Vlasenko wrote:
> With this change, "iowait-ness" of every idle period is decided
> at the moment it starts:
> if this CPU's run-queue had tasks waiting on I/O, then this idle
> period's duration will be added to iowait_sleeptime.
>
> This fixes the bug where iowait and/or idle counts could go backwards,
> but iowait accounting is not precise (it can show more iowait
> that there really is).
>
NAK on this, the thing going backwards is a symptom of the bug, not an
actual bug itself.
next prev parent reply other threads:[~2014-05-07 14:23 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-07 13:41 [PATCH 1/4] nohz: Only update sleeptime stats locally Denys Vlasenko
2014-05-07 13:41 ` [PATCH 2/4] nohz: Synchronize sleep time stats with seqlock Denys Vlasenko
2014-05-07 13:41 ` [PATCH 3/4 v2] nohz: Fix idle/iowait counts going backwards Denys Vlasenko
2014-05-07 14:23 ` Peter Zijlstra [this message]
2014-05-07 16:49 ` Denys Vlasenko
2014-05-07 16:56 ` Peter Zijlstra
2014-05-07 18:24 ` Denys Vlasenko
2014-05-07 19:06 ` Peter Zijlstra
2014-05-07 13:41 ` [PATCH 4/4 v2] nohz: Fix iowait overcounting if iowait task migrates Denys Vlasenko
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