From: Jan Kara Subject: Re: [RFC][PATCH] set_page_buffer_dirty should skip unmapped buffers Date: Mon, 11 Sep 2006 11:46:42 +0200 Message-ID: <20060911094641.GA3336@atrey.karlin.mff.cuni.cz> References: <20060906153449.GC18281@atrey.karlin.mff.cuni.cz> <1157559545.23501.30.camel@dyn9047017100.beaverton.ibm.com> <20060906162723.GA14345@atrey.karlin.mff.cuni.cz> <1157563016.23501.39.camel@dyn9047017100.beaverton.ibm.com> <20060906172733.GC14345@atrey.karlin.mff.cuni.cz> <1157641877.7725.13.camel@dyn9047017100.beaverton.ibm.com> <20060907223048.GD22549@atrey.karlin.mff.cuni.cz> <4500F2B2.4010204@us.ibm.com> <20060908082531.GA28397@atrey.karlin.mff.cuni.cz> <45017FAA.1070203@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andrew Morton , Anton Altaparmakov , sct@redhat.com, linux-fsdevel , lkml , ext4 Return-path: Received: from atrey.karlin.mff.cuni.cz ([195.113.31.123]:6808 "EHLO atrey.karlin.mff.cuni.cz") by vger.kernel.org with ESMTP id S932191AbWIKJrG (ORCPT ); Mon, 11 Sep 2006 05:47:06 -0400 To: Badari Pulavarty Content-Disposition: inline In-Reply-To: <45017FAA.1070203@us.ibm.com> Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Hi, > >>>Original commit code assumes, that when a buffer on BJ_SyncData list is > >>>locked, > >>>it is being written to disk. But this is not true and hence it can lead > >>>to a > >>>potential data loss on crash. Also the code didn't count with the fact > >>>that > >>>journal_dirty_data() can steal buffers from committing transaction and > >>>hence > >>>could write buffers that no longer belong to the committing transaction. > >>>Finally it could possibly happen that we tried writing out one buffer > >>>several > >>>times. > >>> > >>>The patch below tries to solve these problems by a complete rewrite of > >>>the data > >>>commit code. We go through buffers on t_sync_datalist, lock buffers > >>>needing > >>>write out and store them in an array. Buffers are also immediately > >>>refiled to > >>>BJ_Locked list or unfiled (if the write out is completed). When the > >>>array is > >>>full or we have to block on buffer lock, we submit all accumulated > >>>buffers for > >>>IO. > >>> > >>>Signed-off-by: Jan Kara > >>> > >>> > >>> > >>I have been running 4+ hours with this patch and seems to work fine. I > >>haven't hit any > >>assert yet :) > >> > >>I will let it run till tomorrow. I will let you know, how it goes. > >> > > Great, thanks. BTW: Do you have any performance tests handy? The > >changes are big enough to cause some unexpected performance regressions, > >livelocks... If you don't have anything ready, I can setup and run > >something myself. Just that I don't like this testing too much ;). > > > Tests are still running fine. > > I don't have any performance tests handy. We have some automated tests I > can schedule to run to verify the stability aspects. OK. I've run IOZONE rewrite throughput test on my computer with iozone -t 10 -i 0 -s 10M -e 2.6.18-rc6 and the same kernel + my patch seem to give almost the same results. The strange thing was that both in vanilla and patched kernel there were several runs where a write througput (when iozone was creating the file) was suddenly 10% of the usual value (18MB/s vs. 2MB/s). The rewrite numbers were always fine. Maybe that has something to do with block allocation code. Anyway, it is not a regression of my patch so unless your test finds some problem I think the patch should be ready for inclusion into -mm... Honza -- Jan Kara SuSE CR Labs