From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58586) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eZMmi-0004NP-7U for qemu-devel@nongnu.org; Wed, 10 Jan 2018 15:15:41 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eZMmd-0002eK-56 for qemu-devel@nongnu.org; Wed, 10 Jan 2018 15:15:40 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59268) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eZMmc-0002dG-AW for qemu-devel@nongnu.org; Wed, 10 Jan 2018 15:15:34 -0500 Date: Wed, 10 Jan 2018 20:15:19 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20180110201519.GF2451@work-vm> References: <20180109153538.GC1197@stefanha-x1.localdomain> <20180109195517.GD2708@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] Some question about savem/qcow2 incremental snapshot List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: "He, Junyan" , "qemu-devel@nongnu.org" , Juan Quintela , John Snow * Stefan Hajnoczi (stefanha@gmail.com) wrote: > On Tue, Jan 9, 2018 at 7:55 PM, Dr. David Alan Gilbert > wrote: > >> Certain guest operations like rebooting or zeroing memory will defeat > >> the incremental guest RAM snapshot feature. It's worth thinking about > >> these cases to make sure this feature would be worth it in real use > >> cases. > > > > But those probably wouldn't upset an NVDimm? > > If the guest dirties all RAM then the incremental snapshot feature > degrades to a full snapshot. I'm asking if there are common > operations where that happens. > > I seem to remember Windows guests zero all pages on cold boot. Maybe > that's not the case anymore. > > Worth checking before embarking on this feature because it could be a > waste of effort if it turns out real-world guests dirty all memory in > common cases. Right, but I'm hoping that there's some magic somewhere where an NVDimm doesn't get zero'd because of a cold boot since that would seem to make it volatile. Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK