From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1EN7Q8-0006po-28 for qemu-devel@nongnu.org; Wed, 05 Oct 2005 07:26:48 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1EN7Q6-0006pL-0X for qemu-devel@nongnu.org; Wed, 05 Oct 2005 07:26:47 -0400 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1EN7Q5-0006p1-BQ for qemu-devel@nongnu.org; Wed, 05 Oct 2005 07:26:45 -0400 Received: from [203.190.192.17] (helo=wasp.net.au) by monty-python.gnu.org with esmtp (Exim 4.34) id 1EN7Q5-0001Hg-54 for qemu-devel@nongnu.org; Wed, 05 Oct 2005 07:26:45 -0400 Message-ID: <4343B896.30806@wasp.net.au> Date: Wed, 05 Oct 2005 15:27:18 +0400 From: Brad Campbell MIME-Version: 1.0 Subject: Re: [Qemu-devel] [patch] non-blocking disk IO References: <4340D479.7030301@stanfordalumni.org> <4342E8B7.8050507@wasp.net.au> <43430A44.7010403@stanfordalumni.org> In-Reply-To: <43430A44.7010403@stanfordalumni.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org John Coiner wrote: > > Thanks for the report. I was able to reproduce this. > > The problem was due to missing Makefile dependencies. The patch modifies > 'block_int.h', which is #included in several '.c' files. The file > 'block.c' recompiled at 'make' time, but 'block-qcow.c' didn't. The > resulting '.o' files had different opinions about what a > BlockDriverState struct looked like, which broke the qcow code. Having had it running for a while I did some performance tests and found no performance gains _at all_, but then I'm running my entire system over the network on an NFS filesystem (this machine has no disks in it). *NOW* having said that, one of the tricks I do to keep qemu from "going to sleep" when running a long process like a big software install (sometimes it appears to stall until I move the mouse around a bit) is to ping the machine constantly from the host. Prior to this patch I would get pings that varied from 1ms to 250ms. With this patch I get a spread from about 1ms to 15ms tops. So it has smoothed out the operation of the host noticably (also noticable in screen redraws and UI responsiveness while under a heavy disk load). No performance for me, but it just "feels" better to use all round. So, no functional regressions, better usability but no performance here (probably due to running the whole thing over nfs) One day I'll get a local disk and test it out. As a lark, I also did a fresh compile of the BOCHS latest CVS bios with the apm and dma patches included. It appears to give me a slight speed improvement on booting my XP guest, but given the nature of my system that could be statistical noise.. If anyone wants to give it a whirl I have put my newly compiled bios here http://fnarfbargle.dyndns.org:81/bios Regards, Brad -- "Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so." -- Douglas Adams