From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755775AbXD0Mu3 (ORCPT ); Fri, 27 Apr 2007 08:50:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755772AbXD0Mu3 (ORCPT ); Fri, 27 Apr 2007 08:50:29 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:37775 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755770AbXD0MuD (ORCPT ); Fri, 27 Apr 2007 08:50:03 -0400 Date: Fri, 27 Apr 2007 14:49:32 +0200 From: Pavel Machek To: Linus Torvalds Cc: Nigel Cunningham , Pekka Enberg , LKML Subject: Re: Back to the future. Message-ID: <20070427124932.GA23513@elf.ucw.cz> References: <1177567481.5025.211.camel@nigel.suspend2.net> <84144f020704260028q190fc90fs8f9ea703e42e7910@mail.gmail.com> <1177573348.5025.224.camel@nigel.suspend2.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > * Doing things in the right order? (Prepare the image, then do the > > atomic copy, then save). > > I'd actually like to discuss this a bit.. > > I'm obviously not a huge fan of the whole user/kernel level split and > interfaces, but I actually do think that there is *one* split that makes > sense: > > - generate the (whole) snapshot image entirely inside the kernel > > - do nothing else (ie no IO at all), and just export it as a single image > to user space (literally just mapping the pages into user space). > *one* interface. None of the "pretty UI update" crap. Just a single > system call: > > void *snapshot_system(u32 *size); > > which will map in the snapshot, return the mapped address and the size > (and if you want to support snapshots > 4GB, be my guest, but I suspect > you're actually *better* off just admitting that if you cannot shrink > the snapshot to less than 32 bits, it's not worth doing) I think this is very similar to current uswsusp design; except that we are using read on /dev/snapshot to read the snapshot (not memory mapping) and that we freeze the system (because I do not think killall _SIGSTOP is enough). Can you confirm that it is indeed similar design, or tell me why I'm wrong? You had some pretty strong words for uswsusp before, so I'd like to understand your position here. ("Ouch, I do not know, I am out of time" is still better reply than silence.) Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html