From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 17 Sep 2008 18:40:08 -0700 From: Andrew Morton Subject: Re: [RFC][PATCH] Remove cgroup member from struct page (v3) Message-Id: <20080917184008.92b7fc4c.akpm@linux-foundation.org> In-Reply-To: <20080917232826.GA19256@balbir.in.ibm.com> References: <200809091500.10619.nickpiggin@yahoo.com.au> <20080909141244.721dfd39.kamezawa.hiroyu@jp.fujitsu.com> <30229398.1220963412858.kamezawa.hiroyu@jp.fujitsu.com> <20080910012048.GA32752@balbir.in.ibm.com> <1221085260.6781.69.camel@nimitz> <48C84C0A.30902@linux.vnet.ibm.com> <1221087408.6781.73.camel@nimitz> <20080911103500.d22d0ea1.kamezawa.hiroyu@jp.fujitsu.com> <48C878AD.4040404@linux.vnet.ibm.com> <20080911105638.1581db90.kamezawa.hiroyu@jp.fujitsu.com> <20080917232826.GA19256@balbir.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: balbir@linux.vnet.ibm.com Cc: KAMEZAWA Hiroyuki , Dave Hansen , Nick Piggin , hugh@veritas.com, menage@google.com, xemul@openvz.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Wed, 17 Sep 2008 16:28:26 -0700 Balbir Singh wrote: > > Before trying the sparsemem approach, I tried a radix tree per node, > per zone and I seemed to actually get some performance > improvement.(1.5% (noise maybe)) > > But please do see and review (tested on my x86_64 box with unixbench > and some other simple tests) > > v4..v3 > 1. Use a radix tree per node, per zone > > v3...v2 > 1. Convert flags to unsigned long > 2. Move page_cgroup->lock to a bit spin lock in flags > > v2...v1 > > 1. Fix a small bug, don't call radix_tree_preload_end(), if preload fails > > This is a rewrite of a patch I had written long back to remove struct page > (I shared the patches with Kamezawa, but never posted them anywhere else). > I spent the weekend, cleaning them up for 2.6.27-rc5-mmotm (29 Aug 2008). > > I've tested the patches on an x86_64 box, I've run a simple test running > under the memory control group and the same test running concurrently under > two different groups (and creating pressure within their groups). > > Advantages of the patch > > 1. It removes the extra pointer in struct page > > Disadvantages > > 1. Radix tree lookup is not an O(1) operation, once the page is known > getting to the page_cgroup (pc) is a little more expensive now. Why are we doing this? I can guess, but I'd rather not have to. a) It's slower. b) It uses even more memory worst-case. c) It uses less memory best-case. someone somewhere decided that (Aa + Bb) / Cc < 1.0. What are the values of A, B and C and where did they come from? ;) (IOW, your changelog is in the category "sucky", along with 90% of the others) -- 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