From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934466AbXGKVH5 (ORCPT ); Wed, 11 Jul 2007 17:07:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934334AbXGKVGd (ORCPT ); Wed, 11 Jul 2007 17:06:33 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:51813 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934330AbXGKVGb (ORCPT ); Wed, 11 Jul 2007 17:06:31 -0400 From: "Rafael J. Wysocki" To: Mark Lord Subject: Re: Hibernation Redesign Date: Wed, 11 Jul 2007 23:14:15 +0200 User-Agent: KMail/1.9.5 Cc: Jeremy Maitin-Shepard , Nigel Cunningham , Miklos Szeredi , a1426z@gawab.com, jeremy@goop.org, pavel@ucw.cz, nickpiggin@yahoo.com.au, linux-kernel@vger.kernel.org, akpm@linux-foundation.org References: <200707081737.21932.a1426z@gawab.com> <87644rcc7a.fsf@jbms.ath.cx> <46954212.7060105@rtr.ca> In-Reply-To: <46954212.7060105@rtr.ca> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200707112314.16500.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, 11 July 2007 22:48, Mark Lord wrote: > Jeremy Maitin-Shepard wrote: > >> > > I'll certainly admit the kexec idea is vaporware currently, but it does > > differ in a significant way from freezer-based approaches, such that I > > don't think it should be referred to as just another implementation of a > > freezer. Specifically, it doesn't require that the "old kernel" be in a > > "consistent" state to a greater extent than suspend to ram; it is the > > case that all of the devices must be quiesced or shut down to some > > extent, but doing this without races and deadlocks (and without the > > freezer) is certainly very, very similar to what needs to be done for > > suspend to ram, which will need to be solved anyway. Unlike the > > existing hibernate approaches, however, it will not be necessary to use > > any of the driver infrastructure once switched to the "save image" > > kernel, and thus it will not matter what locks are held, for instance. > > I really doubt that kexec(a special kernel) is going to solve anything here. > The new kernel will have to initialize, probe for devices, etc. > Which will take time. > Which will slow down hibernate to an unacceptable degree. > Right now, it (TuxOnIce) is *very* fast. > Adding 10 seconds or so for reprobing/resetting/reiniting devices > is not going to be useful. > And modifying all of the drivers to *not* do their usual probe sequence > sounds rather intrusive and is likely also a non-starter here. > > Or is it? Well, we're going to change what the drivers do during hibernation for other reasons, so it may well be non-issue. Still, we can only speculate until it's done. Which is why I think that the present discussion is premature. Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth