From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id 0F49C6B02A4 for ; Fri, 30 Jul 2010 11:44:09 -0400 (EDT) Received: from d01relay03.pok.ibm.com (d01relay03.pok.ibm.com [9.56.227.235]) by e9.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id o6UFRBaY031251 for ; Fri, 30 Jul 2010 11:27:11 -0400 Received: from d01av03.pok.ibm.com (d01av03.pok.ibm.com [9.56.224.217]) by d01relay03.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o6UFhwfx286116 for ; Fri, 30 Jul 2010 11:43:58 -0400 Received: from d01av03.pok.ibm.com (loopback [127.0.0.1]) by d01av03.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id o6UFhvMK005076 for ; Fri, 30 Jul 2010 12:43:58 -0300 Subject: Re: [PATCH] Tight check of pfn_valid on sparsemem - v4 From: Dave Hansen In-Reply-To: References: <20100728155617.GA5401@barrios-desktop> <20100728225756.GA6108@barrios-desktop> <20100729161856.GA16420@barrios-desktop> <20100729170313.GB16420@barrios-desktop> <20100729183320.GH18923@n2100.arm.linux.org.uk> <1280436919.16922.11246.camel@nimitz> <20100729221426.GA28699@n2100.arm.linux.org.uk> <1280450338.16922.11735.camel@nimitz> Content-Type: text/plain; charset="ANSI_X3.4-1968" Date: Fri, 30 Jul 2010 08:43:54 -0700 Message-ID: <1280504634.16922.14449.camel@nimitz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Christoph Lameter Cc: Russell King - ARM Linux , Minchan Kim , KAMEZAWA Hiroyuki , Milton Miller , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Mel Gorman , Johannes Weiner , Kukjin Kim List-ID: On Fri, 2010-07-30 at 07:48 -0500, Christoph Lameter wrote: > On Thu, 29 Jul 2010, Dave Hansen wrote: > > > SPARSEMEM_EXTREME would be a bit different. It's a 2-level lookup. > > You'd have 16 "section roots", each representing 256MB of address space. > > Each time we put memory under one of those roots, we'd fill in a > > 512-section second-level table, which is designed to always fit into one > > page. If you start at 256MB, you won't waste all those entries. > > That is certain a solution to the !MMU case and it would work very much > like a page table. If you have an MMU then the vmemmap sparsemem > configuration can take advantage of of that to avoid the 2 level lookup. Yup, couldn't agree more, Christoph. It wouldn't hurt to have several them available on ARM since the architecture is so diverse. -- Dave -- 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