Re: [PATCH 3/4 v2] nohz: Fix idle/iowait counts going backwards

From: Peter Zijlstra
Date: Wed May 07 2014 - 10:23:42 EST


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.
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