From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763989AbZEHUx0 (ORCPT ); Fri, 8 May 2009 16:53:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1763053AbZEHUw6 (ORCPT ); Fri, 8 May 2009 16:52:58 -0400 Received: from terminus.zytor.com ([198.137.202.10]:55799 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761638AbZEHUw5 (ORCPT ); Fri, 8 May 2009 16:52:57 -0400 Message-ID: <4A049B99.4000402@zytor.com> Date: Fri, 08 May 2009 13:52:41 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Andi Kleen CC: Jan Beulich , mingo@elte.hu, tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86-64: improve e820_search_gap() References: <4A0199B8.76EA.0078.0@novell.com> <4A03BC1A.9060605@zytor.com> <4A03F016.76EA.0078.0@novell.com> <874ovvo0wo.fsf@basil.nowhere.org> <4A0492EA.6080403@zytor.com> <20090508205347.GC23223@one.firstfloor.org> In-Reply-To: <20090508205347.GC23223@one.firstfloor.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andi Kleen wrote: > On Fri, May 08, 2009 at 01:15:38PM -0700, H. Peter Anvin wrote: >> Andi Kleen wrote: >>> "Jan Beulich" writes: >>>> Why blindly? Aren't hotpluggable memory ranges supposed to be reserved >>>> in the E820 map? >>> They are supposed to be reserved in SRAT, but not in e820. >> Ah, okay. Perhaps we should fold this information into our internal >> "e820" map? If so I guess the question is how soon we can do that. > > You could do that or just query SRAT too, but ... > > The problem is really that there are still systems which have hidden > holes which are not reserved anywhere. When I last hacked on the gap algorithm > it triggered subtle bugs. So this will never be fully reliable. > That's without a question. However, as far as querying SRAT, I don't like the idea of spreading the knowledge of the system memory map out between a bunch of different places, each of which have a little piece of the puzzle. It puts a huge onus on the user to know what mechanisms are actually available, and really makes a shitty interface. -hpa