From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760767AbXGFEDX (ORCPT ); Fri, 6 Jul 2007 00:03:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751374AbXGFEDQ (ORCPT ); Fri, 6 Jul 2007 00:03:16 -0400 Received: from nigel.suspend2.net ([203.171.70.205]:52148 "EHLO nigel.suspend2.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750814AbXGFEDP (ORCPT ); Fri, 6 Jul 2007 00:03:15 -0400 From: Nigel Cunningham To: Benjamin Herrenschmidt Subject: Re: [PATCH] Remove process freezer from suspend to RAM pathway Date: Fri, 6 Jul 2007 14:03:15 +1000 User-Agent: KMail/1.9.6 Cc: Pavel Machek , "Rafael J. Wysocki" , Matthew Garrett , linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org, Alan Stern References: <20070703042916.GA17240@srcf.ucam.org> <200707060935.12706.nigel@nigel.suspend2.net> <1183694055.3388.108.camel@localhost.localdomain> In-Reply-To: <1183694055.3388.108.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1936548.jGbeEE64qb"; protocol="application/pgp-signature"; micalg=pgp-sha1 Content-Transfer-Encoding: 7bit Message-Id: <200707061403.15932.nigel@nigel.suspend2.net> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org --nextPart1936548.jGbeEE64qb Content-Type: text/plain; charset="cp 850" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Hi. On Friday 06 July 2007 13:54:15 Benjamin Herrenschmidt wrote: > On Fri, 2007-07-06 at 09:35 +1000, Nigel Cunningham wrote: > >=20 > > Nice try :) Okay then, you remove the freezer, try hibernating, then ge= t=20 back=20 > > to me after you've fixed your filesystem because some process that wasn= 't=20 > > frozen started writing things after the atomic copy (making the on disk= =20 > > filesystem inconsistent with the snapshot). > >=20 > > As Pavel rightly said, you can get rid of the freezer, but you're only= =20 going=20 > > to have to implement another one that does the essentially the same thi= ng,=20 > > even if it is at some other level. >=20 > I was mostly talking about STR... Regarding STD, we have a different > problem and we all know it. The freezer is one somewhat horrible way to > get it working for now, I would prefer something more along the way that > blocks the page cache from writing out new dirty pages though, except > those specifically flagged by the snapshot. >=20 > That is, some kind of proper snapshotting facility, as linus was > describing some time ago. The kind of thing Linus was talking about would limit you (as swsusp and=20 uswsusp do now) to only half the amount of memory. I suppose you could lzf= =20 compress as you did the snapshot. That would generally get you up to 2/3rds= ,=20 but then again you can't know what compression ratio you'll get until you=20 try, so reliability would suffer or it would take longer because of retryin= g. I/O from swsusp and suspend2 use bios directly, so the page cache isn't an= =20 issue for them (apart from the fact that Suspend2 saves the page cache=20 separately so it can get a full image). Not sure about uswsusp. Only having half the amount of memory doesn't sound like a big limitation f= or=20 modern desktops & laptops, but don't forget that there are embedded guys=20 wanting to hbernate too :) Regards, Nigel =2D-=20 Nigel Cunningham Christian Reformed Church of Cobden 103 Curdie Street, Cobden 3266, Victoria, Australia Ph. +61 3 5595 1185 / +61 417 100 574 Communal Worship: 11 am Sunday. --nextPart1936548.jGbeEE64qb Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQBGjb8DN0y+n1M3mo0RAnlCAJ0YB1WRNez65mvawvFVrbih2oE9lgCg1drl Aa/O8qLc5htNjOLfHBJ87ls= =ZQRS -----END PGP SIGNATURE----- --nextPart1936548.jGbeEE64qb--