From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1KdBeR-0006dF-Bu for qemu-devel@nongnu.org; Tue, 09 Sep 2008 18:25:35 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1KdBeN-0006ci-5E for qemu-devel@nongnu.org; Tue, 09 Sep 2008 18:25:34 -0400 Received: from [199.232.76.173] (port=54427 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1KdBeN-0006cf-1q for qemu-devel@nongnu.org; Tue, 09 Sep 2008 18:25:31 -0400 Received: from mail2.shareable.org ([80.68.89.115]:46225) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1KdBeM-0008BL-Bj for qemu-devel@nongnu.org; Tue, 09 Sep 2008 18:25:31 -0400 Date: Tue, 9 Sep 2008 23:25:19 +0100 From: Jamie Lokier Subject: Re: [Qemu-devel] [PATCH 7/10] Switch the memory savevm handler to be "live" Message-ID: <20080909222519.GA13022@shareable.org> References: <1220989802-13706-1-git-send-email-aliguori@us.ibm.com> <1220989802-13706-8-git-send-email-aliguori@us.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1220989802-13706-8-git-send-email-aliguori@us.ibm.com> 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 Cc: Chris Wright , Uri Lublin , Anthony Liguori , kvm@vger.kernel.org Anthony Liguori wrote: > This patch replaces the static memory savevm/loadvm handler with a > "live" one. This handler is used even if performing a non-live > migration. Excellent. One of the annoyances of savevm currently is it pauses the VM for a significant time, so you can't use it to snapshot production systems being used. > The key difference between this handler and the previous is that each page is > prefixed with the address of the page. The QEMUFile rate limiting code, in > combination with the live migration dirty tracking bits, is used to determine > which pages should be sent and how many should be sent. > > The live save code "converges" when the number of dirty pages > reaches a fixed amount. Currently, this is 10 pages. This is > something that should eventually be derived from whatever the > bandwidth limitation is. Does this mean that a snapshot could record the same page many times, perhaps even unbounded, while the guest is dirtying pages at a high rate? Or is the guest dirtying rate limited too to ensure the file writer will converge in bounded time? Thanks, -- Jamie