linux-kernel - Re: [PATCH] mm fix page writeback accounting to fix oom condition under heavy I/O

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Message-ID: <alpine.LFD.2.00.0902092120450.3048@localhost.localdomain>
Date:	Mon, 9 Feb 2009 21:23:56 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Jens Axboe <jens.axboe@...cle.com>, akpm@...ux-foundation.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, thomas.pi@...or.dea,
	Yuriy Lalym <ylalym@...il.com>, ltt-dev@...ts.casi.polymtl.ca,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm fix page writeback accounting to fix oom condition
 under heavy I/O



On Mon, 9 Feb 2009, Mathieu Desnoyers wrote:
> 
> So this patch fixes this behavior by only decrementing the page accounting
> _after_ the block I/O writepage has been done.

This makes no sense, really.

Or rather, I don't mind the notion of updating the counters only after IO 
per se, and _that_ part of it probably makes sense. But why is it that you 
only then fix up two of the call-sites. There's a lot more call-sites than 
that for this function. 

So if this really makes a big difference, that's an interesting starting 
point for discussion, but I don't see how this particular patch could 
possibly be the right thing to do.

			Linus
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