Date: Thu, 29 Dec 2005 11:12:57 +0200 (EET)
From: Pekka J Enberg <penberg@cs.Helsinki.FI>
To: cai <junjiec@gmail.com>
cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>,
       linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [RFC][fat] use mpage_readpage when cluster size is page-alignment
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On Thu, 29 Dec 2005, cai wrote:
> > I am not sure I am following you. Shouldn't do_mpage_readpage work for
> > all adjacent blocks regardless of whether block size is page-aligned
> > or not? What's is the performance problem you're thinking of?
>  
> no, not block size but cluster size
> as you know, in FAT, file is organized in clusters
> and one cluster could have N blocks(sectors).
> so if cluster size is not page-aligned,
> a page may live in non-adjacent blocks, and
> do_mpage_readpage has to fall back to block_read_full_page
> in this case.

But the non-page-aligned clusters can be adjacent on disk, no? Besides, I 
don't think there's enough overhead in do_mpage_readpage for the 
non-adjacent case to justify keeping the non-mpage version around.

				Pekka
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