Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755385Ab2HUJZZ (ORCPT ); Tue, 21 Aug 2012 05:25:25 -0400 Received: from mx2.parallels.com ([64.131.90.16]:39261 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752200Ab2HUJZW (ORCPT ); Tue, 21 Aug 2012 05:25:22 -0400 Message-ID: <50335341.6010400@parallels.com> Date: Tue, 21 Aug 2012 13:22:09 +0400 From: Glauber Costa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 MIME-Version: 1.0 To: Michal Hocko CC: , , , , Johannes Weiner , Andrew Morton , , Christoph Lameter , David Rientjes , Pekka Enberg , Pekka Enberg , Suleiman Souhlal Subject: Re: [PATCH v2 09/11] memcg: propagate kmem limiting information to children References: <1344517279-30646-1-git-send-email-glommer@parallels.com> <1344517279-30646-10-git-send-email-glommer@parallels.com> <20120817090005.GC18600@dhcp22.suse.cz> <502E0BC3.8090204@parallels.com> <20120817093504.GE18600@dhcp22.suse.cz> <502E17C4.7060204@parallels.com> <20120817103550.GF18600@dhcp22.suse.cz> <502E1E90.1080805@parallels.com> <20120821075430.GA19797@dhcp22.suse.cz> In-Reply-To: <20120821075430.GA19797@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2215 Lines: 46 On 08/21/2012 11:54 AM, Michal Hocko wrote: > On Fri 17-08-12 14:36:00, Glauber Costa wrote: >> On 08/17/2012 02:35 PM, Michal Hocko wrote: >>>>> But I never said that can't happen. I said (ok, I meant) the static >>>>> branches can't be disabled. >>> Ok, then I misunderstood that because the comment was there even before >>> static branches were introduced and it made sense to me. This is >>> inconsistent with what we do for user accounting because even if we set >>> limit to unlimitted we still account. Why should we differ here? >> >> Well, we account even without a limit for user accounting. This is a >> fundamental difference, no ? > > Yes, user memory accounting is either on or off all the time (switchable > at boot time). > My understanding of kmem is that the feature is off by default because > it brings an overhead that is worth only special use cases. And that > sounds good to me. I do not see a good reason to have runtime switch > off. It makes the code more complicated for no good reason. E.g. how do > you handle charges you left behind? Say you charged some pages for > stack? > Answered in your other e-mail. About the code complication, yes, it does make the code more complicated. See below. > But maybe you have a good use case for that? > Honestly, I don't. For my particular use case, this would be always on, and end of story. I was operating under the belief that being able to say "Oh, I regret", and then turning it off would be beneficial, even at the expense of the - self contained - complication. For the general sanity of the interface, it is also a bit simpler to say "if kmem is unlimited, x happens", which is a verifiable statement, than to have a statement that is dependent on past history. But all of those need of course, as you pointed out, to be traded off by the code complexity. I am fine with either, I just need a clear sign from you guys so I don't keep deimplementing and reimplementing this forever. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/