From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263852AbTJ1EiV (ORCPT ); Mon, 27 Oct 2003 23:38:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263855AbTJ1EiV (ORCPT ); Mon, 27 Oct 2003 23:38:21 -0500 Received: from mail-03.iinet.net.au ([203.59.3.35]:64913 "HELO mail.iinet.net.au") by vger.kernel.org with SMTP id S263852AbTJ1EiT (ORCPT ); Mon, 27 Oct 2003 23:38:19 -0500 Message-ID: <3F9DF0D3.60707@cyberone.com.au> Date: Tue, 28 Oct 2003 15:30:11 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030827 Debian/1.4-3 X-Accept-Language: en MIME-Version: 1.0 To: Michael Frank CC: cliff white , linux-kernel@vger.kernel.org, Nigel Cunningham Subject: Re: 2.6.0-test8/test9 io scheduler needs tuning? References: <200310261201.14719.mhf@linuxmail.org> <20031027145531.2eb01017.cliffw@osdl.org> <3F9DAF2C.8010308@cyberone.com.au> <200310281213.31709.mhf@linuxmail.org> In-Reply-To: <200310281213.31709.mhf@linuxmail.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Michael Frank wrote: >On Tuesday 28 October 2003 07:50, Nick Piggin wrote: > >>cliff white wrote: >> >> >>>On Tue, 28 Oct 2003 05:52:45 +0800 >>>Michael Frank wrote: >>> >>> >>> >>>>To my surprise 2.6 - which used to do better then 2.4 - does no longer >>>>handle these test that well. >>>> >>>>Generally, IDE IO throughput is _very_ uneven and IO _stops_ at times with the >>>>system cpu load very high (and the disk LED off). >>>> >>>>IMHO the CPU scheduling is OK but the IO scheduling acts up here. >>>> >>>>The test system is a 2.4GHz P4 with 512M RAM and a 55MB/s udma IDE harddisk. >>>> >>>>The tests load the system to loadavg > 30. IO should be about 20MB/s on avg. >>>> >>>>Enclosed are vmstat -1 logs for 2.6-test9-Vanilla, followed by 2.6-test8-Vanilla >>>>(-mm1 behaves similar), 2.4.22-Vanilla and 2.4.21+swsusp all compiled wo preempt. >>>> >>>>IO on 2.6 stops now for seconds at a time. -test8 is worse than -test9 >>>> >>>> >>>We see the same delta at OSDL. Try repeating your tests with 'elevator=deadline' >>>to confirm. >>>For example, on the 8-cpu platform: >>>STP id Kernel Name MaxJPM Change Options >>>281669 linux-2.6.0-test8 7014.42 0.0 >>>281671 linux-2.6.0-test8 8294.94 +18.26% elevator=deadline >>> >>>The -mm kernels don't show this big delta. We also do not see this delta on >>>smaller machines >>> >>> >>I'm working with Randy to fix this. Attached is what I have so far. See how >>you go with it. >> >> >> > >This has been done without running a kernel compile, by $ ti-tests/ti stat ub17 ddw 4 5000 > >Seems to be more even on average but still drops IO too low and then gets overloaded. > >By "too low" I mean io bo less than 10000. > >By overloaded I mean io bo goes much above 40000. The disk can do maybe 60000. > >When io bo is much above 40000, cpu scheduling is being impaired as indicated >by vmstat stopping output for a second or so... > The bi / bo fields in vmstat aren't exactly what the disk is doing, rather the requests the queue is taking. The interesting thing is how your final measurement compares with 2.4. I think 2.4 has quite a lot more free requests by default (512 vs 128 for 2.6). This might also be causing Nigel's writeout problems perhaps. Try echo 512 > /sys/block/xxx/queue/nr_requests