From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id B7DBC6B02A4 for ; Thu, 29 Jul 2010 15:55:59 -0400 (EDT) Date: Thu, 29 Jul 2010 14:55:53 -0500 (CDT) From: Christoph Lameter Subject: Re: [PATCH] Tight check of pfn_valid on sparsemem - v4 In-Reply-To: <20100729183320.GH18923@n2100.arm.linux.org.uk> 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Russell King - ARM Linux Cc: 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, Russell King - ARM Linux wrote: > And no, setting the sparse section size to 512kB doesn't work - memory is > offset by 256MB already, so you need a sparsemem section array of 1024 > entries just to cover that - with the full 256MB populated, that's 512 > unused entries followed by 512 used entries. That too is going to waste > memory like nobodies business. SPARSEMEM EXTREME does not handle that? Some ARMs seem to have MMUs. If so then use SPARSEMEM_VMEMMAP. You can map 4k pages for the mmap through a page table. Redirect unused 4k blocks to the NULL page. -- 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