From: OGAWA Hirofumi Subject: Re: [PATCHSET v3.1 0/7] data integrity: Stabilize pages during writeback for various fses Date: Wed, 11 May 2011 01:12:13 +0900 Message-ID: <87zkmupmaq.fsf@devron.myhome.or.jp> 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> <20110510145421.GJ4402@quack.suse.cz> Mime-Version: 1.0 Content-Type: text/plain Cc: "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 To: Jan Kara Return-path: Received: from mail.parknet.co.jp ([210.171.160.6]:49768 "EHLO mail.parknet.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756583Ab1EJQMT (ORCPT ); Tue, 10 May 2011 12:12:19 -0400 In-Reply-To: <20110510145421.GJ4402@quack.suse.cz> (Jan Kara's message of "Tue, 10 May 2011 16:54:21 +0200") Sender: linux-ext4-owner@vger.kernel.org List-ID: Jan Kara writes: >> 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... Maybe possible, but you really think on usual case just blocking is better? Thanks. -- OGAWA Hirofumi