From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1DYAmp-0003Oz-8e for qemu-devel@nongnu.org; Tue, 17 May 2005 18:43:39 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1DYAmn-0003NQ-Fj for qemu-devel@nongnu.org; Tue, 17 May 2005 18:43:37 -0400 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1DYAmm-0003N8-6b for qemu-devel@nongnu.org; Tue, 17 May 2005 18:43:36 -0400 Received: from [12.124.108.50] (helo=dash.soliddesign.net) by monty-python.gnu.org with esmtp (Exim 4.34) id 1DY90r-0008TZ-Aa for qemu-devel@nongnu.org; Tue, 17 May 2005 16:50:01 -0400 Subject: Re: [Qemu-devel] Re: request : qemu-smp as target From: Joe Batt In-Reply-To: <200505172121.28546.paul@codesourcery.com> References: <4285EC1E.4090904@bellard.org> <1116089712.18405.14.camel@fred.ofc.soliddesign.net> <200505172121.28546.paul@codesourcery.com> Content-Type: text/plain Date: Tue, 17 May 2005 15:41:34 -0500 Message-Id: <1116362494.20056.50.camel@fred.ofc.soliddesign.net> Mime-Version: 1.0 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: Paul Brook Cc: qemu-devel@nongnu.org On Tue, 2005-05-17 at 21:21 +0100, Paul Brook wrote: > > What inter processor synchronization issues are there? Could you take > > this a step further and use processes on different machines for each > > processor? (There are many shared memory implementations to choose > > from.) Are there so many resources shared > > between the CPUs to make this a ridiculous proposition? > > Baically most SMP/shared memory systems assume very low latency communication > between CPUs and memory. For example on opteron systems remote memory latency > is of the order of 200 cpu cycles. Typical ethernet latency is several > million cycles. But how often will the virtual CPUs need the same page and is there any other shared resource other than memory? I don't know how independent each CPU is. Though in side discussions, everyone agrees with you, I haven't seen numbers to convince my gut. If page only needs to be faulted back and forth every couple million cycles, then it might work. > The only solution I can imagine being even vaguely worthwhile is a running > user-mode qemu on top of a native openmozix system. OpenMosix is very interesting, but is a pain to setup. How about this: ssh -f host1 qemu -cpu-server $KEY ssh -f host2 qemu -cpu-server $KEY qemu -cpu-client host1:$KEY \ -cpu-client host2:$KEY \ -hda server.image > > I have ignorantly implemented an SH2 emulator, > > Cool. Any chance you're going to make these changes publicly available? It was a Java implementation for a customer. Not my property and not integrated with any free software. > Paul -- Joe Batt