From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753664AbYHINji (ORCPT ); Sat, 9 Aug 2008 09:39:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751919AbYHINj3 (ORCPT ); Sat, 9 Aug 2008 09:39:29 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:60787 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751800AbYHINj2 (ORCPT ); Sat, 9 Aug 2008 09:39:28 -0400 Subject: Re: [RFC][PATCH 1/4] checkpoint-restart: general infrastructure From: Dave Hansen To: Arnd Bergmann Cc: containers@lists.linux-foundation.org, Theodore Tso , linux-kernel@vger.kernel.org, Oren Laadan In-Reply-To: <200808090837.07417.arnd@arndb.de> References: <20080807224033.FFB3A2C1@kernel> <200808090039.20289.arnd@arndb.de> <1218242614.19082.65.camel@nimitz> <200808090837.07417.arnd@arndb.de> Content-Type: text/plain Date: Sat, 09 Aug 2008 06:39:25 -0700 Message-Id: <1218289165.19082.74.camel@nimitz> Mime-Version: 1.0 X-Mailer: Evolution 2.22.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2008-08-09 at 08:37 +0200, Arnd Bergmann wrote: > On Saturday 09 August 2008, Dave Hansen wrote: > > On Sat, 2008-08-09 at 00:39 +0200, Arnd Bergmann wrote: > > > The main problem I see with that would be atomicity: If you want multiple > > > processes to keep interacting with each other, you need to save them at > > > the same point in time, which gets harder as you split your interface into > > > more than a single file descriptor. > > > > It could take ages to write out a checkpoint even to a single fd, so I > > suspect we'd have the exact same kinds of issues either way. > > I guess either way, you have to SIGSTOP (or similar) all the tasks you want > to checkpoint atomically before you start saving the contents. > If you use a single fd, you can do that under the covers, when using a > more complex file system, it seems more logical to require an explicit > interface for this. Oh, we're already working on patches to the freezer code to do this for us. There's a branch in here from Matt H. that's doing just that: http://git.kernel.org/?p=linux/kernel/git/daveh/linux-2.6-next-lxc.git;a=shortlog -- Dave