From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758223AbYHIGhr (ORCPT ); Sat, 9 Aug 2008 02:37:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751799AbYHIGhi (ORCPT ); Sat, 9 Aug 2008 02:37:38 -0400 Received: from moutng.kundenserver.de ([212.227.126.177]:62144 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751729AbYHIGhh (ORCPT ); Sat, 9 Aug 2008 02:37:37 -0400 From: Arnd Bergmann To: Dave Hansen Subject: Re: [RFC][PATCH 1/4] checkpoint-restart: general infrastructure Date: Sat, 9 Aug 2008 08:37:07 +0200 User-Agent: KMail/1.9.9 Cc: containers@lists.linux-foundation.org, Theodore Tso , linux-kernel@vger.kernel.org, Oren Laadan References: <20080807224033.FFB3A2C1@kernel> <200808090039.20289.arnd@arndb.de> <1218242614.19082.65.camel@nimitz> In-Reply-To: <1218242614.19082.65.camel@nimitz> X-Face: I@=L^?./?$U,EK.)V[4*>`zSqm0>65YtkOe>TFD'!aw?7OVv#~5xd\s,[~w]-J!)|%=]>=?utf-8?q?+=0A=09=7EohchhkRGW=3F=7C6=5FqTmkd=5Ft=3FLZC=23Q-=60=2E=60Y=2Ea=5E?= =?utf-8?q?3zb?=) =?utf-8?q?+U-JVN=5DWT=25cw=23=5BYo0=267C=26bL12wWGlZi=0A=09=7EJ=3B=5Cwg?= =?utf-8?q?=3B3zRnz?=,J"CT_)=\H'1/{?SR7GDu?WIopm.HaBG=QYj"NZD_[zrM\Gip^U MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200808090837.07417.arnd@arndb.de> X-Provags-ID: V01U2FsdGVkX1/nfSRRjiKLtyP332W25pGw3UQIopQrMVHjg2F T4s6CL4GQgv/0M8LgSeN/EPQs8njeduO6VEd7Pz8tcUmxhFkmM mUOz2WFY9hdeXshG/RB5Q== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Arnd <><