linux-kernel - Re: per-bdi-throttling: synchronous writepage doesn't work correctly

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Message-Id: <1193935886.27652.313.camel@twins>
Date:	Thu, 01 Nov 2007 17:51:26 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	jdike@...toit.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: per-bdi-throttling: synchronous writepage doesn't work
	correctly

On Thu, 2007-11-01 at 17:49 +0100, Miklos Szeredi wrote:
> Hi,
> 
> It looks like bdi_thresh will always be zero if filesystem does
> synchronous writepage, resulting in very poor write performance.
> 
> Hostfs (UML) is one such example, but there might be others.
> 
> The only solution I can think of is to add a set_page_writeback();
> end_page_writeback() pair (or some reduced variant, that only does
> the proportions magic).  But that means auditing quite a few
> filesystems...

Ouch...

I take it there is no other function that is shared between all these
writeout paths which we could stick a bdi_writeout_inc(bdi) in?



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