From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965287AbXDMXDz (ORCPT ); Fri, 13 Apr 2007 19:03:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965672AbXDMXDz (ORCPT ); Fri, 13 Apr 2007 19:03:55 -0400 Received: from nigel.suspend2.net ([203.171.70.205]:58329 "EHLO nigel.suspend2.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965287AbXDMXDy (ORCPT ); Fri, 13 Apr 2007 19:03:54 -0400 Subject: Re: [RFD] swsusp problem: Drivers allocate much memory during suspend (was: Re: 2.6.21-rc5: swsusp: Not enough free memory) From: Nigel Cunningham To: "Rafael J. Wysocki" Cc: Pavel Machek , Jiri Slaby , Linux kernel mailing list , linux-pm@lists.osdl.org In-Reply-To: <200704140057.35829.rjw@sisk.pl> References: <460B6E4B.3060004@gmail.com> <20070413224053.GT28264@elf.ucw.cz> <1176504306.7112.206.camel@nigel.suspend2.net> <200704140057.35829.rjw@sisk.pl> Content-Type: text/plain Date: Sat, 14 Apr 2007 09:03:50 +1000 Message-Id: <1176505430.7112.216.camel@nigel.suspend2.net> Mime-Version: 1.0 X-Mailer: Evolution 2.10.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi. On Sat, 2007-04-14 at 00:57 +0200, Rafael J. Wysocki wrote: > > > > Well, I'm not sure. First, we don't really know what the value of it should be > > > > and this alone is a good enough reason for making it tunable, IMHO. Second, I > > > > think different systems may need different PAGES_FOR_IO and taking just the > > > > maximum (even if we learn how much that actually is) seems to be wasteful in > > > > > > Well, it is wasteful as in "we save slightly smaller image than we > > > could". That's okay with me. > > > > No. If the driver can't allocate the memory, your call to device_suspend > > will fail. This isn't about image size but about success or failure to > > hibernate. > > If we take PAGES_FOR_IO to be the maximum over all possible configurations > that can hibernate, the majority of systems will just create smaller images than > they could have created for smaller PAGES_FOR_IO, but all of them will be > able to hibernate. :-) You also use PAGES_FOR_IO in enough_free_mem. Say you set it to the 9000 pages I mentioned before (35M). On a machine with 64 megabytes of memory, you'll never be able to suspend because you'll never satisfy free > nr_pages + PAGES_FOR_IO + meta I'll freely admit that 64 megabytes is tiny nowadays, but it's not completely unknown. The point is really that you're effectively making swsusp unusable for machines with RAM < (PAGES_FOR_IO * (say) 3). But what do you set PAGES_FOR_IO to? There'll always be someone with $WHIZ_BANG_CONFIG who is pushing to have the value increased, and every increase knocks out more of your lowend users. Regards, Nigel