From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 18 Sep 2008 13:43:04 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [RFC][PATCH] Remove cgroup member from struct page (v3) Message-Id: <20080918134304.93985542.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20080917184008.92b7fc4c.akpm@linux-foundation.org> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: balbir@linux.vnet.ibm.com, 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 18:40:08 -0700 Andrew Morton wrote: > > 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? ;) > Balbir, don't you like pre-allocate-page-cgroup-at-boot at all ? I don't like radix-tree for objects which can spread to very vast/sparse area ;) BTW, I already have lazy-lru-by-pagevec protocol on my patch(hash version) and seems to work well. I'm now testing it and will post today if I'm enough lucky. Thanks, -Kame -- 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