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Date: Fri, 06 Sep 2002 10:03:05 -0700
From: Andrew Morton <akpm@zip.com.au>
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To: Rik van Riel <riel@conectiva.com.br>
CC: linux-kernel@vger.kernel.org, Linus Torvalds <torvalds@transmeta.com>
Subject: Re: [PATCH] iowait stats for 2.5.33
References: <Pine.LNX.4.44L.0209061332190.1857-100000@imladris.surriel.com>
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Rik van Riel wrote:
> 
> Hi,
> 
> the following patch, against 2.5.33-mm4, implements iowait
> statistics in /proc/stat.

trivial:  I'd be inclined to use:

void iowait_schedule()
{
	atomic_inc(...);
	schedule();
	atomic_dec(...);
}

less trivial: there are times when an io wait is deliberate:
in the context of balance_dirty_pages(), and (newly) in the
context of page reclaim when current->backing_dev_info is
non-zero.

Given that this is a deliberate throttling sleep, perhaps it
should not be included in the accounting?   That way we only
account for the accidental, undesirable sleeps, and reads
and such.
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