From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx180.postini.com [74.125.245.180]) by kanga.kvack.org (Postfix) with SMTP id 6880B6B005D for ; Tue, 21 Aug 2012 05:25:22 -0400 (EDT) Message-ID: <50335341.6010400@parallels.com> Date: Tue, 21 Aug 2012 13:22:09 +0400 From: Glauber Costa MIME-Version: 1.0 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: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, devel@openvz.org, Johannes Weiner , Andrew Morton , kamezawa.hiroyu@jp.fujitsu.com, Christoph Lameter , David Rientjes , Pekka Enberg , Pekka Enberg , Suleiman Souhlal 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org