From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH v6 0/4] ext4: Coordinate data-only flush requests sent by fsync Date: Tue, 30 Nov 2010 17:43:01 +0100 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 Return-path: Content-Disposition: inline In-Reply-To: <20101130113906.176ffcad@notabene.brown> Sender: linux-ext4-owner@vger.kernel.org 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 List-Id: dm-devel.ids 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.