From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753410Ab1LTCQy (ORCPT ); Mon, 19 Dec 2011 21:16:54 -0500 Received: from mail-ww0-f44.google.com ([74.125.82.44]:55157 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751551Ab1LTCQw (ORCPT ); Mon, 19 Dec 2011 21:16:52 -0500 Date: Tue, 20 Dec 2011 06:16:47 +0400 From: Anton Vorontsov To: Michal Hocko Cc: KOSAKI Motohiro , Arve =?utf-8?B?SGrDuG5uZXbDpWc=?= , Rik van Riel , Pavel Machek , Greg Kroah-Hartman , Andrew Morton , David Rientjes , John Stultz , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Johannes Weiner , KAMEZAWA Hiroyuki Subject: Re: Android low memory killer vs. memory pressure notifications Message-ID: <20111220021647.GB4531@oksana.dev.rtsoft.ru> References: <20111219025328.GA26249@oksana.dev.rtsoft.ru> <20111219121255.GA2086@tiehlicka.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20111219121255.GA2086@tiehlicka.suse.cz> 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 Mon, Dec 19, 2011 at 01:12:55PM +0100, Michal Hocko wrote: > [Didn't get to the patch yet but a comment on memcg] > > On Mon 19-12-11 06:53:28, Anton Vorontsov wrote: > [...] > > - Use memory controller cgroup (CGROUP_MEM_RES_CTLR) notifications from > > the kernel side, plus userland "manager" that would kill applications. > > > > The main downside of this approach is that mem_cg needs 20 bytes per > > page (on a 32 bit machine). So on a 32 bit machine with 4K pages > > that's approx. 0.5% of RAM, or, in other words, 5MB on a 1GB machine. > > page_cgroup is 16B per page and with the current Johannes' memcg > naturalization work (in the mmotm tree) we are down to 8B per page (we > got rid of lru). Kamezawa has some patches to get rid of the flags so we > will be down to 4B per page on 32b. Is this still too much? > I would be really careful about a yet another lowmem notification > mechanism. 4 bytes (1MB wastage on a 1GB machine) sounds much better. If there are no other downsides of using cgroups-based low memory killer, then maybe it's not worth doing yet another low memory notification stuff. > > 0.5% doesn't sound too bad, but 5MB does, quite a little bit. So, > > mem_cg feels like an overkill for this simple task (see the driver at > > the very bottom). > > Why is it an overkill? I think that having 2 groups (active and > inactive) and move tasks between then sounds quite elegant. Yep, that was the original idea. But back then mem_cg was way too costly, so nobody seriously considered this as a solution. Thanks, -- Anton Vorontsov Email: cbouatmailru@gmail.com