From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id A97126B02A4 for ; Fri, 30 Jul 2010 08:48:06 -0400 (EDT) Date: Fri, 30 Jul 2010 07:48:00 -0500 (CDT) From: Christoph Lameter 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org 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 List-ID: 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, 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