From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753278Ab2IZUFr (ORCPT ); Wed, 26 Sep 2012 16:05:47 -0400 Received: from mx2.parallels.com ([64.131.90.16]:33810 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752533Ab2IZUFp (ORCPT ); Wed, 26 Sep 2012 16:05:45 -0400 Message-ID: <50635F46.7000700@parallels.com> Date: Thu, 27 Sep 2012 00:02:14 +0400 From: Glauber Costa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120911 Thunderbird/15.0.1 MIME-Version: 1.0 To: Tejun Heo CC: Michal Hocko , , , , , , Suleiman Souhlal , Frederic Weisbecker , Mel Gorman , David Rientjes , Johannes Weiner Subject: Re: [PATCH v3 04/13] kmem accounting basic infrastructure References: <1347977050-29476-5-git-send-email-glommer@parallels.com> <20120926140347.GD15801@dhcp22.suse.cz> <20120926163648.GO16296@google.com> <50633D24.6020002@parallels.com> <50634105.8060302@parallels.com> <20120926180124.GA12544@google.com> <50634FC9.4090609@parallels.com> <20120926193417.GJ12544@google.com> <50635B9D.8020205@parallels.com> <20120926195648.GA20342@google.com> In-Reply-To: <20120926195648.GA20342@google.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [109.173.3.27] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/26/2012 11:56 PM, Tejun Heo wrote: > Hello, > > On Wed, Sep 26, 2012 at 11:46:37PM +0400, Glauber Costa wrote: >> Besides not being part of cgroup core, and respecting very much both >> cgroups' and basic sanity properties, kmem is an actual feature that >> some people want, and some people don't. There is no reason to believe >> that applications that want will live in the same environment with ones >> that don't want. > > I don't know. It definitely is less crazy than .use_hierarchy but I > wouldn't say it's an inherently different thing. I mean, what does it > even mean to have u+k limit on one subtree and not on another branch? > And we worry about things like what if parent doesn't enable it but > its chlidren do. > It is inherently different. To begin with, it actually contemplates two use cases. It is not a work around. The meaning is also very well defined. The meaning of having this enabled in one subtree and not in other is: Subtree A wants to track kernel memory. Subtree B does not. It's that, and never more than that. There is no maybes and no buts, no magic knobs that makes it behave in a crazy way. If a children enables it but the parent does not, this does what every tree does: enable it from that point downwards. > This is a feature which adds complexity. If the feature is necessary > and justified, sure. If not, let's please not and let's err on the > side of conservativeness. We can always add it later but the other > direction is much harder. > I disagree. Having kmem tracking adds complexity. Having to cope with the use case where we turn it on dynamically to cope with the "user page only" use case adds complexity. But I see no significant complexity being added by having it per subtree. Really. You have the use_hierarchy fiasco in mind, and I do understand that you are raising the flag and all that. But think in terms of functionality: This thing here is a lot more similar to swap than use_hierarchy. Would you argue that memsw should be per-root ? The reason why it shouldn't: Some people want to limit memory consumption all the way to the swap, some people don't. Same with kmem. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH v3 04/13] kmem accounting basic infrastructure Date: Thu, 27 Sep 2012 00:02:14 +0400 Message-ID: <50635F46.7000700@parallels.com> References: <1347977050-29476-5-git-send-email-glommer@parallels.com> <20120926140347.GD15801@dhcp22.suse.cz> <20120926163648.GO16296@google.com> <50633D24.6020002@parallels.com> <50634105.8060302@parallels.com> <20120926180124.GA12544@google.com> <50634FC9.4090609@parallels.com> <20120926193417.GJ12544@google.com> <50635B9D.8020205@parallels.com> <20120926195648.GA20342@google.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120926195648.GA20342@google.com> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Tejun Heo Cc: Michal Hocko , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com, devel@openvz.org, linux-mm@kvack.org, Suleiman Souhlal , Frederic Weisbecker , Mel Gorman , David Rientjes , Johannes Weiner On 09/26/2012 11:56 PM, Tejun Heo wrote: > Hello, > > On Wed, Sep 26, 2012 at 11:46:37PM +0400, Glauber Costa wrote: >> Besides not being part of cgroup core, and respecting very much both >> cgroups' and basic sanity properties, kmem is an actual feature that >> some people want, and some people don't. There is no reason to believe >> that applications that want will live in the same environment with ones >> that don't want. > > I don't know. It definitely is less crazy than .use_hierarchy but I > wouldn't say it's an inherently different thing. I mean, what does it > even mean to have u+k limit on one subtree and not on another branch? > And we worry about things like what if parent doesn't enable it but > its chlidren do. > It is inherently different. To begin with, it actually contemplates two use cases. It is not a work around. The meaning is also very well defined. The meaning of having this enabled in one subtree and not in other is: Subtree A wants to track kernel memory. Subtree B does not. It's that, and never more than that. There is no maybes and no buts, no magic knobs that makes it behave in a crazy way. If a children enables it but the parent does not, this does what every tree does: enable it from that point downwards. > This is a feature which adds complexity. If the feature is necessary > and justified, sure. If not, let's please not and let's err on the > side of conservativeness. We can always add it later but the other > direction is much harder. > I disagree. Having kmem tracking adds complexity. Having to cope with the use case where we turn it on dynamically to cope with the "user page only" use case adds complexity. But I see no significant complexity being added by having it per subtree. Really. You have the use_hierarchy fiasco in mind, and I do understand that you are raising the flag and all that. But think in terms of functionality: This thing here is a lot more similar to swap than use_hierarchy. Would you argue that memsw should be per-root ? The reason why it shouldn't: Some people want to limit memory consumption all the way to the swap, some people don't. Same with kmem. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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