From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266704AbUFYU5E (ORCPT ); Fri, 25 Jun 2004 16:57:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266745AbUFYU5E (ORCPT ); Fri, 25 Jun 2004 16:57:04 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.103]:17630 "EHLO e3.ny.us.ibm.com") by vger.kernel.org with ESMTP id S266704AbUFYU4q (ORCPT ); Fri, 25 Jun 2004 16:56:46 -0400 Subject: Re: [Lhms-devel] Re: Merging Nonlinear and Numa style memory hotplug From: Dave Hansen To: Yasunori Goto Cc: Linux Kernel ML , Linux Hotplug Memory Support , Linux-Node-Hotplug , linux-mm , "BRADLEY CHRISTIANSEN [imap]" In-Reply-To: <20040625121110.2937.YGOTO@us.fujitsu.com> References: <20040625114720.2935.YGOTO@us.fujitsu.com> <1088189973.29059.231.camel@nighthawk> <20040625121110.2937.YGOTO@us.fujitsu.com> Content-Type: text/plain Message-Id: <1088196895.29059.357.camel@nighthawk> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Fri, 25 Jun 2004 13:54:55 -0700 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Whoops. Hit CTRL-Enter during my ASCII art :) On Fri, 2004-06-25 at 13:45, Yasunori Goto wrote: > > > Are you sure that all architectures need phys_section? > > > > You don't *need* it, but the alternative is a scan of the mem_section[] > > array, which would be much, much slower. > > > > Do you have an idea for an alternate implementation? > > I didn't find that scan of the mem_section[] is necessary. > I thought just that mem_section index = phys_section index. > May I ask why scan of mem_section is necessary? > I might still have misunderstood something. For now, the indexes happen to be the same. However, for discontiguous memory systems, this will not be the case Consider a system with 3 GB of RAM, 2GB@0x00000000 and 1 GB@0xC0000000 with 1 GB sections. The arrays would look like this: mem | phys ----+----- 0 | 0 1 | 1 2 | 3 See the B-lpfn patch that I posted today for why this is important. It basically allows us to represent sparse physical addresses in a much more linear fashion. -- Dave