linux-kernel - Re: [PATCH] VFS: Pagecache usage optimization on pagesize !=blocksize environment

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Date:	Mon, 26 May 2008 13:40:49 +0200
From:	Jan Kara <jack@...e.cz>
To:	Hisashi Hifumi <hifumi.hisashi@....ntt.co.jp>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] VFS: Pagecache usage optimization on pagesize
	!=blocksize environment

On Mon 26-05-08 16:20:10, Hisashi Hifumi wrote:
> 
> >  But I'm slightly confused that the patch helps because I've always
> >thought that mpage_readpage() (which is what we end up calling from
> >do_generic_mapping_read()) always reads the whole page. Thus either all
> >buffers in the page or none of them are uptodate... So what do I miss
> >here?
> >
> >								Honza
> 
> On ext3/4, a file is written through buffer/block. So if a page has multiple 
> buffers, buffers can be uptodate partially especially under random write workloads.
> See __block_prepare_write and __block_commit_write.
  Ah, I see. Thanks for explanation.

									Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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