Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932625Ab1EJOyZ (ORCPT ); Tue, 10 May 2011 10:54:25 -0400 Received: from cantor2.suse.de ([195.135.220.15]:46564 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752436Ab1EJOyY (ORCPT ); Tue, 10 May 2011 10:54:24 -0400 Date: Tue, 10 May 2011 16:54:21 +0200 From: Jan Kara To: OGAWA Hirofumi Cc: Jan Kara , "Darrick J. Wong" , Theodore Tso , Alexander Viro , Jens Axboe , "Martin K. Petersen" , Jeff Layton , Dave Chinner , linux-kernel , Dave Hansen , Christoph Hellwig , linux-mm@kvack.org, Chris Mason , Joel Becker , linux-scsi , linux-fsdevel , linux-ext4@vger.kernel.org, Mingming Cao Subject: Re: [PATCHSET v3.1 0/7] data integrity: Stabilize pages during writeback for various fses Message-ID: <20110510145421.GJ4402@quack.suse.cz> References: <20110509230318.19566.66202.stgit@elm3c44.beaverton.ibm.com> <87tyd31fkc.fsf@devron.myhome.or.jp> <20110510123819.GB4402@quack.suse.cz> <87hb924s2x.fsf@devron.myhome.or.jp> <20110510132953.GE4402@quack.suse.cz> <878vue4qjb.fsf@devron.myhome.or.jp> <87zkmu3b2i.fsf@devron.myhome.or.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87zkmu3b2i.fsf@devron.myhome.or.jp> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1784 Lines: 40 On Tue 10-05-11 23:05:41, OGAWA Hirofumi wrote: > OGAWA Hirofumi writes: > > > Jan Kara writes: > > > >>> I see. So many block layer stuff sounds like broken on corner case? If > >>> so, I more feel this approach should be temporary workaround, and should > >>> use another less-blocking approach. > >> Not many but some... The alternative to less blocking approach is to do > >> copy-out before a page is submitted for IO (or various middle ground > >> alternatives of doing sometimes copyout, sometimes blocking...). That costs > >> some performance as well. We talked about it at LSF and the approach > >> Darrick is implementing was considered the least intrusive. There's really > >> no way to fix these corner cases and keep performance. > > > > You already considered, to copy only if page was writeback (like > > copy-on-write). I.e. if page is on I/O, copy, then switch the page for > > writing new data. > > missed question mark in here. > > Did you already consider, to copy only if page was writeback (like > copy-on-write)? I.e. if page is on I/O, copy, then switch the page for > writing new data. Yes, that was considered as well. We'd have to essentially migrate the page that is under writeback and should be written to. You are going to pay the cost of page allocation, copy, increased memory & cache pressure. Depending on your backing storage and workload this may or may not be better than waiting for IO... Honza -- Jan Kara SUSE Labs, CR -- 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/