Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753947Ab0K3Qnh (ORCPT ); Tue, 30 Nov 2010 11:43:37 -0500 Received: from verein.lst.de ([213.95.11.210]:46034 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751164Ab0K3Qnf (ORCPT ); Tue, 30 Nov 2010 11:43:35 -0500 Date: Tue, 30 Nov 2010 17:43:01 +0100 From: Christoph Hellwig To: Neil Brown Cc: "Darrick J. Wong" , Jens Axboe , "Theodore Ts'o" , Andreas Dilger , Alasdair G Kergon , Jan Kara , Mike Snitzer , linux-kernel , linux-raid@vger.kernel.org, Keith Mannthey , dm-devel@redhat.com, Mingming Cao , Tejun Heo , linux-ext4@vger.kernel.org, Ric Wheeler , Christoph Hellwig , Josef Bacik Subject: Re: [PATCH v6 0/4] ext4: Coordinate data-only flush requests sent by fsync Message-ID: <20101130164301.GB30858@lst.de> References: <20101129220536.12401.16581.stgit@elm3b57.beaverton.ibm.com> <20101130113906.176ffcad@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101130113906.176ffcad@notabene.brown> User-Agent: Mutt/1.3.28i X-Spam-Score: 0 () Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 943 Lines: 20 On Tue, Nov 30, 2010 at 11:39:06AM +1100, Neil Brown wrote: > Would it not be sufficient to simply gather flushes while a flush is pending. > i.e > - if no flush is pending, set the 'flush pending' flag, submit a flush, > then clear the flag. > - if a flush is pending, then wait for it to complete, and then submit a > single flush on behalf of all pending flushes. > > That way when flush is fast, you do a flush every time, and when it is slow > you gather multiple flushes together. We can even optimize the second flush away if no other I/O has completed since the first flush has started. That will always be the case for SATA devices as the cache flush command is not queued. -- 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/