From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753531Ab2GPN3y (ORCPT ); Mon, 16 Jul 2012 09:29:54 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:42141 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753458Ab2GPN3v (ORCPT ); Mon, 16 Jul 2012 09:29:51 -0400 Date: Mon, 16 Jul 2012 15:29:35 +0200 From: Pavel Machek To: Adrian Hunter Cc: Arnd Bergmann , linaro-kernel@lists.linaro.org, linux-mm@kvack.org, "Luca Porzio (lporzio)" , Alex Lemberg , linux-kernel@vger.kernel.org, Saugata Das , Venkatraman S , Yejin Moon , Hyojin Jeong , "linux-mmc@vger.kernel.org" , kernel-team@android.com, "Rafael J. Wysocki" Subject: Re: swap on eMMC and other flash Message-ID: <20120716132935.GA20549@elf.ucw.cz> References: <201203301744.16762.arnd@arndb.de> <201203301850.22784.arnd@arndb.de> <4F7C3CE2.5070803@intel.com> <201204041247.53289.arnd@arndb.de> <4F855CD7.1000902@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4F855CD7.1000902@intel.com> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 2012-04-11 13:28:39, Adrian Hunter wrote: > On 04/04/12 15:47, Arnd Bergmann wrote: > > On Wednesday 04 April 2012, Adrian Hunter wrote: > >> On 30/03/12 21:50, Arnd Bergmann wrote: > >>> (sorry for the duplicated email, this corrects the address of the android > >>> kernel team, please reply here) > >>> > >>> On Friday 30 March 2012, Arnd Bergmann wrote: > >>> > >>> We've had a discussion in the Linaro storage team (Saugata, Venkat and me, > >>> with Luca joining in on the discussion) about swapping to flash based media > >>> such as eMMC. This is a summary of what we found and what we think should > >>> be done. If people agree that this is a good idea, we can start working > >>> on it. > >> > >> There is mtdswap. > > > > Ah, very interesting. I wasn't aware of that. Obviously we can't directly > > use it on block devices that have their own garbage collection and wear > > leveling built into them, but it's interesting to see how this was solved > > before. > > > > While we could build something similar that remaps blocks between an > > eMMC device and the logical swap space that is used by the mm code, > > my feeling is that it would be easier to modify the swap code itself > > to do the right thing. > > > >> Also the old Nokia N900 had swap to eMMC. > >> > >> The last I heard was that swap was considered to be simply too slow on hand > >> held devices. > > > > That's the part that we want to solve here. It has nothing to do with > > handheld devices, but more with specific incompatibilities of the > > block allocation in the swap code vs. what an eMMC device expects > > to see for fast operation. If you write data in the wrong order on > > flash devices, you get long delays that you don't get when you do > > it the right way. The same problem exists for file systems, and is > > being addressed there as well. > > > >> As systems adopt more RAM, isn't there a decreasing demand for swap? > > > > No. You would never be able to make hibernate work, no matter how much > > RAM you add ;-) > > Have you considered making hibernate work without swap? It does work without swap. See userland suspend packages, where you write the image is up-to you. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html