Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932186Ab0G3MsK (ORCPT ); Fri, 30 Jul 2010 08:48:10 -0400 Received: from smtp109.prem.mail.ac4.yahoo.com ([76.13.13.92]:41824 "HELO smtp109.prem.mail.ac4.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1758548Ab0G3MsG (ORCPT ); Fri, 30 Jul 2010 08:48:06 -0400 X-Yahoo-SMTP: _Dag8S.swBC1p4FJKLCXbs8NQzyse1SYSgnAbY0- X-YMail-OSG: ywuPkEcVM1laTJfgBxOeMihDpPjj0gn1U7pHLqQVCuZFTgi 8jvzQrPssrN1hdG6PiwwFQlxG6gSz.dxWfv2QLADbcDISksCerlG37pOkJBC XmnkEt6YS39KLdyx37dWM7Xs9OYkqV17Aw6NrJG.9zHgOdTreLc64NbPhMD. 1PAh6PO9DMjEUZhYcfPRItAw3_4rvMAMzXLhy9cWeSLxBO_vj5kudDDgwE29 tFwBwS2ij5IIzP9hlN5DKPcBM_d0Uf0OmcnRLHWYlO456hO0P X-Yahoo-Newman-Property: ymail-3 Date: Fri, 30 Jul 2010 07:48:00 -0500 (CDT) From: Christoph Lameter X-X-Sender: cl@router.home To: Dave Hansen 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 Subject: Re: [PATCH] Tight check of pfn_valid on sparsemem - v4 In-Reply-To: <1280450338.16922.11735.camel@nimitz> Message-ID: 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> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 851 Lines: 16 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/