From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sd0109e.au.ibm.com (d23rh905.au.ibm.com [202.81.18.225]) by e23smtp02.au.ibm.com (8.13.1/8.13.1) with ESMTP id m8I44Jo5019960 for ; Thu, 18 Sep 2008 14:08:34 +1000 Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by sd0109e.au.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id m8I3wG1Y168680 for ; Thu, 18 Sep 2008 13:58:32 +1000 Received: from d23av03.au.ibm.com (loopback [127.0.0.1]) by d23av03.au.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m8I3wGC3003253 for ; Thu, 18 Sep 2008 13:58:16 +1000 Message-ID: <48D1D1C2.9060204@linux.vnet.ibm.com> Date: Wed, 17 Sep 2008 20:57:54 -0700 From: Balbir Singh Reply-To: balbir@linux.vnet.ibm.com MIME-Version: 1.0 Subject: Re: [RFC][PATCH] Remove cgroup member from struct page (v3) 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> <20080917184008.92b7fc4c.akpm@linux-foundation.org> In-Reply-To: <20080917184008.92b7fc4c.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton 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: Andrew Morton wrote: > 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) Yes, I agree, to be honest we discussed the reasons on the mailing list and those should go to the changelog. I'll do that in the next version of the patches. These are early RFC patches, but the changelog does suck. -- Balbir -- 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