From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755292AbYEZLk7 (ORCPT ); Mon, 26 May 2008 07:40:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754258AbYEZLkw (ORCPT ); Mon, 26 May 2008 07:40:52 -0400 Received: from styx.suse.cz ([82.119.242.94]:55520 "EHLO mail.suse.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754213AbYEZLkv (ORCPT ); Mon, 26 May 2008 07:40:51 -0400 Date: Mon, 26 May 2008 13:40:49 +0200 From: Jan Kara To: Hisashi Hifumi Cc: Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH] VFS: Pagecache usage optimization on pagesize !=blocksize environment Message-ID: <20080526114049.GA32407@duck.suse.cz> References: <6.0.0.20.2.20080513205758.03a7a6b0@172.19.0.2> <20080521001930.202446eb.akpm@linux-foundation.org> <6.0.0.20.2.20080522160939.051ca938@172.19.0.2> <20080522010355.32590474.akpm@linux-foundation.org> <20080523225133.GB30591@atrey.karlin.mff.cuni.cz> <6.0.0.20.2.20080526155336.058ed7b0@172.19.0.2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6.0.0.20.2.20080526155336.058ed7b0@172.19.0.2> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 SUSE Labs, CR