From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765219AbXGKW1F (ORCPT ); Wed, 11 Jul 2007 18:27:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762673AbXGKW0x (ORCPT ); Wed, 11 Jul 2007 18:26:53 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:52182 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757621AbXGKW0w (ORCPT ); Wed, 11 Jul 2007 18:26:52 -0400 From: "Rafael J. Wysocki" To: Al Boldi Subject: Re: Hibernation Redesign Date: Thu, 12 Jul 2007 00:34:12 +0200 User-Agent: KMail/1.9.5 Cc: Mark Lord , Jeremy Maitin-Shepard , Nigel Cunningham , Miklos Szeredi , 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> <46954212.7060105@rtr.ca> <200707120117.24549.a1426z@gawab.com> In-Reply-To: <200707120117.24549.a1426z@gawab.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200707120034.14201.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thursday, 12 July 2007 00:17, Al Boldi wrote: > Mark Lord wrote: > > Jeremy Maitin-Shepard wrote: > > > I'll certainly admit the kexec idea is vaporware currently, > > Your idea is starting to become a reality with this thread: > "[PATCH 0/2] Kexec jump: The first step to kexec base hibernation" > > > > 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, it's definitely less intrusive than readying drivers for the freezer. There's nothing like this! Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth