linux-kernel - Re: [PATCH] writeback: safety margin for bdi stat errors

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Message-ID: <4CFE7015.3070000@redhat.com>
Date:	Tue, 07 Dec 2010 12:34:13 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Theodore Ts'o" <tytso@....edu>,
	Chris Mason <chris.mason@...cle.com>,
	Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.cz>,
	Jens Axboe <axboe@...nel.dk>, Mel Gorman <mel@....ul.ie>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Christoph Hellwig <hch@....de>, linux-mm <linux-mm@...ck.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] writeback: safety margin for bdi stat errors

On 12/07/2010 08:11 AM, Wu Fengguang wrote:

> So the root cause is, the bdi_dirty is well under nr_dirty due to
> accounting errors. They should be very close because there is only one
> heavy dirtied bdi in the system. This can be fixed by using
> bdi_stat_sum(), however that's costly on large NUMA machines. So do a
> less costly fix of lowering the bdi limit, so that the accounting
> errors won't lead to the absurd situation "global limit exceeded but
> bdi limit not exceeded".
>
> CC: Rik van Riel<riel@...hat.com>
> CC: Peter Zijlstra<a.p.zijlstra@...llo.nl>
> Signed-off-by: Wu Fengguang<fengguang.wu@...el.com>

I like this simple approach.

Acked-by: Rik van Riel <riel@...hat.com>

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