From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753724AbYIVOy4 (ORCPT ); Mon, 22 Sep 2008 10:54:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753315AbYIVOyp (ORCPT ); Mon, 22 Sep 2008 10:54:45 -0400 Received: from e2.ny.us.ibm.com ([32.97.182.142]:42554 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753257AbYIVOyo (ORCPT ); Mon, 22 Sep 2008 10:54:44 -0400 Subject: Re: [PATCH 9/13] memcg: lookup page cgroup (and remove pointer from struct page) From: Dave Hansen To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "balbir@linux.vnet.ibm.com" , "nishimura@mxp.nes.nec.co.jp" , "xemul@openvz.org" , LKML In-Reply-To: <20080922201206.e73d9ce6.kamezawa.hiroyu@jp.fujitsu.com> References: <20080922195159.41a9d2bc.kamezawa.hiroyu@jp.fujitsu.com> <20080922201206.e73d9ce6.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain Date: Mon, 22 Sep 2008 07:52:56 -0700 Message-Id: <1222095177.8533.14.camel@nimitz> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2008-09-22 at 20:12 +0900, KAMEZAWA Hiroyuki wrote: > + /* we don't need too large hash */ > + default_pcg_hash_size = (max_pfn/ENTS_PER_CHUNK); > + default_pcg_hash_size *= 2; > + /* if too big, use automatic calclation */ > + if (default_pcg_hash_size > 1024 * 1024) > + default_pcg_hash_size = 0; > + > + pcg_hashtable = alloc_large_system_hash("PageCgroup Hash", > + sizeof(struct pcg_hash_head), > + default_pcg_hash_size, > + 13, > + 0, > + &pcg_hashshift, > + &pcg_hashmask, > + 0); The one thing I don't see here is much explanation about how large this structure will get. Basing it on max_pfn makes me nervous because of what it will do on machines with very sparse memory. Is this like sparsemem where the structure can be small enough to actually span all of physical memory, or will it be a large memory user? Can you lay out how much memory this will use on a machine like Dave Miller's which has 1GB of memory at 0x0 and 1GB of memory at 1TB up in the address space? Also, how large do the hash buckets get in the average case? -- Dave