From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1FfwtE-0002It-Ng for qemu-devel@nongnu.org; Tue, 16 May 2006 06:34:56 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1FfwtB-0002GK-FH for qemu-devel@nongnu.org; Tue, 16 May 2006 06:34:55 -0400 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1FfwtB-0002G8-9E for qemu-devel@nongnu.org; Tue, 16 May 2006 06:34:53 -0400 Received: from [195.252.0.52] (helo=zebra.uas.se) by monty-python.gnu.org with esmtp (Exim 4.52) id 1Ffwvn-0004YA-DZ for qemu-devel@nongnu.org; Tue, 16 May 2006 06:37:35 -0400 Received: from [127.0.0.1] ([195.252.0.249]) by zebra.uas.se (PMDF V6.0-24 #39208) with ESMTP id <01M2HNDKDTV8000E9Y@zebra.uas.se> for qemu-devel@nongnu.org; Tue, 16 May 2006 12:34:48 +0200 Date: Tue, 16 May 2006 12:34:48 +0200 From: Dan Sandberg Subject: Re: [Qemu-devel] w98se slow with kqemu, apparently some systems only In-reply-to: <200605141624.39231.mr@ramendik.ru> Message-id: <4469AAC8.6000608@medsci.uu.se> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7BIT References: <200605141624.39231.mr@ramendik.ru> 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 Mikhail Ramendik wrote: >Hello, > >There seems to be an issue with guest Windows 98 SE on qemu 0.8.1 and kqemu >1.3.0pre7, on a Linux host. > >Windows 98 SE is visibly very slow; and when qemu is run with -no-kqemu, it is >actually faster. > >I have this issue on two different systems: > >- Intel Celeron 2400 CPU, 512M RAM, RH9-derived, kernel 2.6.11 with some >patches including -ck >- AMD Duron 650 CPU, 256M RAM, Debian sarge, vanilla kernel 2.6.15 (run with >-m 64) > >On the Intel system I also installed NT 4.0 (in a different image) and it is >fast with kqemu. (It has mouse problems - invisible wall, erratic behaviour, >all intermittent - but I know this issue is quite different and patches >exist). > >This same issue was also reported on the user forum: >http://qemu.dad-answers.com/viewtopic.php?t=1476 > >However, other people on IRC have reported that Win98SE is fast for them. In >fact I have transferred my Win98SE image to another person, who runs qemu CVS >and kqemu 1.3.0pre7 on Ubunto dapper; he reported that it runs fast. > >This seems to be an issue on some systems only, but I could not isolate the >key setup difference. I would be most interested in helping to pinpoint the >problem. I am ready to run any tests/patches, and I have an archive of >various old Windows systems (backups...) that I can try on request; I can >also pull CVS if necessary. > > > I can report the same thing with Windows XP host and Windows 98 guest on an Pentium M 1,8 GHz. With Qemu 0.8.1 Windows 98 now runs quite well in normal emulated mode on this computer and actually much slower with kqemu service running. Linux guests run faster with kqemu as it is supposed to be. I still cannot use the -kernel-kqemu option on Windows XP host, but I guess that is known issue. Just a wild guess: Could the combination of Windows 98's memory management and the Soft-MMU for kqemu generate badly aligned memory blocks? The Delphi compiler that I am used to adds its own memory management to guarantee properly aligned memory blocks with realloc() etc for the best possible cache performance (I believe all block requests are automatically aligned by 256-byte as default, at least it should be 8 byte=64-bit). Does anyone know how gcc do? Does it simply call the OS routine? And how does the soft-MMU do it? It is possible to read/write 16/32/64-bit data from a badly aligned buffer, but it can create a serious performance penalty so maybe there is a potential for speed improvements by doing it similar to the way Borland does. Regards Dan