Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 11 Apr 2002 18:57:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 11 Apr 2002 18:57:38 -0400 Received: from h24-67-14-151.cg.shawcable.net ([24.67.14.151]:20987 "EHLO webber.adilger.int") by vger.kernel.org with ESMTP id ; Thu, 11 Apr 2002 18:57:38 -0400 From: Andreas Dilger Date: Thu, 11 Apr 2002 16:55:36 -0600 To: Andrew Morton Cc: Alexander Viro , Linus Torvalds , linux-kernel@vger.kernel.org Subject: Re: [prepatch] address_space-based writeback Message-ID: <20020411225536.GE8062@turbolinux.com> Mail-Followup-To: Andrew Morton , Alexander Viro , Linus Torvalds , linux-kernel@vger.kernel.org In-Reply-To:

<3CB5FFB5.693E7755@zip.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.27i X-GPG-Key: 1024D/0D35BED6 X-GPG-Fingerprint: 7A37 5D79 BF1B CECA D44F 8A29 A488 39F5 0D35 BED6 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Apr 11, 2002 14:27 -0700, Andrew Morton wrote: > One thing I'm not clear on with the private metadata address_space > concept: how will it handle blocksize less than PAGE_CACHE_SIZE? > The only means we have at present of representing sub-page > segments is the buffer_head. Do we want to generalise the buffer > layer so that it can be applied against private address_spaces? > That wouldn't be a big leap. I was going to send you an email on this previously, but I (think I) didn't in the end... At one time Linus proposed having an array of dirty bits for a page, which would allow us to mark only parts of a page dirty (say down to the sector level). I believe this was in the discussion about moving the block devices to the page cache around 2.4.10. While that isn't a huge win in the most cases (it costs the same to write 512 bytes as 4096 bytes to disk because of disk latencies) it may be more important if/when we ever have larger pages. This also becomes more important if you are working with a network filesystem where you have to send all of the dirty data over a much smaller pipe, so sending 512 bytes takes 1/8 as long as sending 4096 bytes. Cheers, Andreas -- Andreas Dilger http://www-mddsp.enel.ucalgary.ca/People/adilger/ http://sourceforge.net/projects/ext2resize/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/