From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NAAVl-00008x-3s for qemu-devel@nongnu.org; Mon, 16 Nov 2009 17:57:29 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NAAVg-00006f-Fo for qemu-devel@nongnu.org; Mon, 16 Nov 2009 17:57:28 -0500 Received: from [199.232.76.173] (port=54528 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NAAVg-00006X-Ak for qemu-devel@nongnu.org; Mon, 16 Nov 2009 17:57:24 -0500 Received: from mail2.shareable.org ([80.68.89.115]:39165) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1NAAVf-0006lm-Or for qemu-devel@nongnu.org; Mon, 16 Nov 2009 17:57:24 -0500 Date: Mon, 16 Nov 2009 22:57:22 +0000 From: Jamie Lokier Subject: Re: [Qemu-devel] QEMU redesigned for MPI (Message Passing Interface) Message-ID: <20091116225722.GF12063@shareable.org> References: <747a56b80911130629q4046b4fbg400f7566997aa931@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Mulyadi Santosa Cc: Victor Vasilchenko , qemu-devel@nongnu.org Mulyadi Santosa wrote: > Hi Victor... > > On 11/13/09, Victor Vasilchenko wrote: > > The only BIG question - what virtualization software can support MPI to > > effectively work on cluster ? > > > > I am asking this question to QEMU team cause I believe QEMU can be the one. > > If you have any ideas or experiments or information - please share with me. > > > > Kind Regards, > > Victor. > > > > If you check through Qemu list archieve, you shall see that there were > more or less similar question: parallelization of Qemu. > Most of the answers are: it can be hardly done. AFAIK, this is due > to how dynamic translation is done... you need (most of the part I > guess) almost 100% serialization. I completely disagree. Dynamic translation doesn't need 100% serialisation, but to relax that it does require atomic ops and memory barriers (including implied ones) in the guest to be translated to equivalents in the host. Unfortunately x86 instructions imply a lot of barriers (program-ordered writes), which is great for programming x86 but not great when translating to non-x86 host code. Right now, though, qemu's translator does not do that, even for x86->x86, so it has to be serialised when running multi-CPU guest code. KVM, on the other hand, does not do dynamic translation and can run multiple threads in parallel because the atomic/barrier semantics are preserved exactly. KVM would be a fine candidate for running multiple threads on different host machines. You'd need to serialise memory using page faults, but such techniques are already implemented with cluster filesystems and writable-mmap'd files, so it might be possible to use KVM over that. -- Jamie