From mboxrd@z Thu Jan 1 00:00:00 1970 From: Badari Pulavarty Subject: Re: [RFC PATCH] ext3 writepage() journal avoidance Date: Thu, 09 Mar 2006 16:45:50 -0800 Message-ID: <4410CC3E.6030905@us.ibm.com> References: <1141929562.21442.4.camel@dyn9047017100.beaverton.ibm.com> <20060309152254.743f4b52.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: sct@redhat.com, jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Ext2-devel@lists.sourceforge.net Return-path: To: Andrew Morton Sender: ext2-devel-admin@lists.sourceforge.net Errors-To: ext2-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: List-Id: linux-fsdevel.vger.kernel.org Andrew Morton wrote: >Badari Pulavarty wrote: > >>I am trying to speed up ext3 writepage() by avoiding >>journaling in non-block allocation cases. Does this >>look reasonable ? So far, my testing is fine. What am >>I missing here ? >> > >Nothing. ext3's writepage(), prepare_write() and commit_write() do often >needlessy open and close transactions when we're doing overwrites. It's >something I've meant to look at for a few years, on and off. > >I'd expect that prepare_write() and commit_write() are more important than >writepage(). > > > >It might be better to test PageMappedToDisk() rather than walking the >buffers. It's certainly faster and it makes optimisation of >prepare_write() and commit_write() easier to handle. > >I'm not sure that PageMappedToDisk() gets set in all the right places >though - it's mainly for the `nobh' handling and block_prepare_write() >would need to be taught to set it. I guess that'd be a net win, even if >only ext3 uses it.. > >Then again, we might be able to speed up block_prepare_write() if >PageMappedToDisk(page). > Makes sense. I will take a look. > >If we go this way we need to be very very careful to keep PG_mappedtodisk >coherent with the state of the buffers. Tricky. We need to think about >whether block_truncate_page() should be clearing PG_mappedtoisk if we did a >partial truncate. > >Don't forget that ext3 supports journalled-mode files on ordered- or >writeback-mounted filesystems, via `chattr +j'. > Wow !! Never knew that. I assume we switch mapping->a_ops for this inode ? >Please be sure to test the >various combinations which that allows when playing with the write paths - >it can trip things up. > >Also be sure to test nobh-mode. > Sure. Thanks for your reply and valuable suggestions. :) Thanks, Badari > ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642