From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx172.postini.com [74.125.245.172]) by kanga.kvack.org (Postfix) with SMTP id 321946B005C for ; Wed, 30 May 2012 10:43:48 -0400 (EDT) Received: from /spool/local by e28smtp08.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 30 May 2012 20:13:45 +0530 Received: from d28av02.in.ibm.com (d28av02.in.ibm.com [9.184.220.64]) by d28relay02.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q4UEhgH55570844 for ; Wed, 30 May 2012 20:13:42 +0530 Received: from d28av02.in.ibm.com (loopback [127.0.0.1]) by d28av02.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q4UKEJmG029906 for ; Thu, 31 May 2012 06:14:20 +1000 From: "Aneesh Kumar K.V" Subject: Re: [PATCH -V6 07/14] memcg: Add HugeTLB extension In-Reply-To: <20120527202848.GC7631@skywalker.linux.vnet.ibm.com> References: <1334573091-18602-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1334573091-18602-8-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20120527202848.GC7631@skywalker.linux.vnet.ibm.com>User-Agent: Notmuch/0.11.1+346~g13d19c3 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) Date: Wed, 30 May 2012 20:13:31 +0530 Message-ID: <87lik920h8.fsf@skywalker.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: linux-mm@kvack.org, mgorman@suse.de, KAMEZAWA Hiroyuki , dhillf@gmail.com, aarcange@redhat.com, mhocko@suse.cz, Andrew Morton , hannes@cmpxchg.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org "Aneesh Kumar K.V" writes: > On Thu, May 24, 2012 at 02:52:26PM -0700, David Rientjes wrote: >> On Mon, 16 Apr 2012, Aneesh Kumar K.V wrote: >> >> > This patch implements a memcg extension that allows us to control HugeTLB >> > allocations via memory controller. The extension allows to limit the >> > HugeTLB usage per control group and enforces the controller limit during >> > page fault. Since HugeTLB doesn't support page reclaim, enforcing the limit >> > at page fault time implies that, the application will get SIGBUS signal if it >> > tries to access HugeTLB pages beyond its limit. This requires the application >> > to know beforehand how much HugeTLB pages it would require for its use. >> > >> > The charge/uncharge calls will be added to HugeTLB code in later patch. >> > Support for memcg removal will be added in later patches. >> > >> >> Again, I disagree with this approach because it's adding the functionality >> to memcg when it's unnecessary; it would be a complete legitimate usecase >> to want to limit the number of globally available hugepages to a set of >> tasks without incurring the per-page tracking from memcg. >> >> This can be implemented as a seperate cgroup and as we move to a single >> hierarchy, you lose no functionality if you mount both cgroups from what >> is done here. >> >> It would be much cleaner in terms of >> >> - build: not requiring ifdefs and dependencies on CONFIG_HUGETLB_PAGE, >> which is a prerequisite for this functionality and is not for >> CONFIG_CGROUP_MEM_RES_CTLR, > > I am not sure we have large number of #ifdef as you have outlined above. > Most of the hugetlb limit code is well isolated already. If we were to > split it as a seperate controller, we will be duplicating code related > cgroup deletion, migration support etc from memcg, because in case > of memcg and hugetlb limit they depend on struct page. So I would expect > we would be end up #ifdef around that code or duplicate them in the > new controller if we were to do hugetlb limit as a seperate controller. > > Another reason for it to be part of memcg is, it is normal to look > at hugetlb usage also as a memory usage. One of the feedback I got > for the earlier post is to see if i can enhace the current code to > make sure memory.usage_in_bytes can also account for hugetlb usage. > People would also like to look at memory.limit_in_bytes to limit total > usage. (inclusive of hugetlb). > >> >> - code: seperating hugetlb bits out from memcg bits to avoid growing >> mm/memcontrol.c beyond its current 5650 lines, and >> > > I can definitely look at spliting mm/memcontrol.c > > >> - performance: not incurring any overhead of enabling memcg for per- >> page tracking that is unnecessary if users only want to limit hugetlb >> pages. >> Since Andrew didn't sent the patchset to Linus because of this discussion, I looked at reworking the patchset as a seperate controller. The patchset I sent here http://thread.gmane.org/gmane.linux.kernel.mm/79230 have seen minimal testing. I also folded the fixup patches Andrew had in -mm to original patchset. Let me know if the changes looks good. -aneesh -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org