From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=58733 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PsHF6-0007IO-FW for qemu-devel@nongnu.org; Wed, 23 Feb 2011 11:07:09 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PsHEz-0000XI-Vt for qemu-devel@nongnu.org; Wed, 23 Feb 2011 11:07:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47037) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PsHEz-0000Wx-Id for qemu-devel@nongnu.org; Wed, 23 Feb 2011 11:07:01 -0500 Message-ID: <4D652FBA.9000104@redhat.com> Date: Wed, 23 Feb 2011 18:03:06 +0200 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [Qemu-devel] Re: Strategic decision: COW format References: <4D5BC467.4070804@redhat.com> <4D5E4271.80501@redhat.com> <4D5E8031.5020402@codemonkey.ws> <4D637A20.9020307@redhat.com> <4D650F10.3060900@redhat.com> <4D651858.9040106@codemonkey.ws> <4D652675.1070908@redhat.com> <4D652868.8030908@codemonkey.ws> <4D6529A9.3090509@redhat.com> <4D652CD3.5030806@codemonkey.ws> In-Reply-To: <4D652CD3.5030806@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Kevin Wolf , Chunqiang Tang , qemu-devel@nongnu.org, Stefan Hajnoczi , Markus Armbruster On 02/23/2011 05:50 PM, Anthony Liguori wrote: >> I still don't see. What would you do with thousands of checkpoints? > > > For reverse debugging, if you store checkpoints at a rate of save, > every 10ms, and then degrade to storing every 100ms after 1 second, > etc. you'll have quite a large number of snapshots pretty quickly. > The idea of snapshotting with reverse debugging is that instead of > undoing every instruction, you can revert to the snapshot before, and > then replay the instruction stream until you get to the desired point > in time. You cannot replay the instruction stream since inputs (interrupts, rdtsc or other timers, I/O) will be different. You need Kemari for this. > > For disaster recovery, there are some workloads that you can > meaningful revert to a snapshot provided that the snapshot is stored > at a rate of something frequency (like once a second). Think of > something like a webserver where the only accumulated data is logs. > Losing some of the logs is better than losing all of the logs. Are static webservers that interesting? For disaster recovery? Anything else will need Kemari. -- error compiling committee.c: too many arguments to function