From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id p0KBDtCR073090 for ; Thu, 20 Jan 2011 05:13:55 -0600 Date: Thu, 20 Jan 2011 06:16:12 -0500 From: Christoph Hellwig Subject: Re: Issues with delalloc->real extent allocation Message-ID: <20110120111612.GA14571@infradead.org> References: <20110114002900.GF16267@dastard> <20110114214334.GN28274@sgi.com> <20110114235549.GI16267@dastard> <20110118204752.GB28791@infradead.org> <20110118231831.GZ28803@dastard> <20110119120321.GC12941@infradead.org> <20110119133147.GN16267@dastard> <20110119135548.GA11502@infradead.org> <20110120013346.GO16267@dastard> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20110120013346.GO16267@dastard> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Dave Chinner Cc: Christoph Hellwig , bpm@sgi.com, xfs@oss.sgi.com On Thu, Jan 20, 2011 at 12:33:46PM +1100, Dave Chinner wrote: > It's case b) that I'm mainly worried about, esp. w.r.t the 64k page > size on ia64/ppc. If we only track a single dirty bit in the page, > then every sub-page, non-appending write to an uncached region of a > file becomes a RMW cycle to initialise the areas around the write > correctly. The question is whether we care about this enough given > that we return at least PAGE_SIZE in stat() to tell applications the > optimal IO size to avoid RMW cycles. Note that this generally is only true for the first write into the region - after that we'll have the rest read into the cache. But we also have the same issue for appending writes if they aren't page aligned. > And if we only do IO on whole pages (i.e regardless of block size) > .writepage suddenly becomes a lot simpler, as well as being trivial > to implement our own .readpage/.readpages.... I don't think it simplifies writepage a lot. All the buffer head handling goes away, but we'll still need to do xfs_bmapi calls at block size granularity. Why would you want to replaced the readpage/readpages code? The generic mpage helpers for it do just fine. _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs