From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qc0-f179.google.com (mail-qc0-f179.google.com [209.85.216.179]) by kanga.kvack.org (Postfix) with ESMTP id D2D0F6B0036 for ; Mon, 13 Jan 2014 20:51:49 -0500 (EST) Received: by mail-qc0-f179.google.com with SMTP id e16so4913735qcx.38 for ; Mon, 13 Jan 2014 17:51:49 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTP id hj7si25591612qeb.78.2014.01.13.17.51.48 for ; Mon, 13 Jan 2014 17:51:49 -0800 (PST) Date: Tue, 14 Jan 2014 09:52:02 +0800 From: Dave Young Subject: Re: [PATCH 2/2] x86, e820 disable ACPI Memory Hotplug if memory mapping is specified by user [v2] Message-ID: <20140114015202.GD4327@dhcp-16-126.nay.redhat.com> References: <1389380698-19361-1-git-send-email-prarit@redhat.com> <1389380698-19361-4-git-send-email-prarit@redhat.com> <52D32962.5050908@redhat.com> <52D4793E.8070102@redhat.com> <1389659632.1792.247.camel@misato.fc.hp.com> <52D48A9D.7000003@zytor.com> <1389661746.1792.254.camel@misato.fc.hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1389661746.1792.254.camel@misato.fc.hp.com> Sender: owner-linux-mm@kvack.org List-ID: To: Toshi Kani Cc: "H. Peter Anvin" , Prarit Bhargava , KOSAKI Motohiro , Bodo Eggert <7eggert@gmx.de>, LKML , Thomas Gleixner , Ingo Molnar , the arch/x86 maintainers , Len Brown , "Rafael J. Wysocki" , Linn Crosetto , Pekka Enberg , Yinghai Lu , Andrew Morton , Tang Chen , Wen Congyang , Vivek Goyal , linux-acpi@vger.kernel.org, "linux-mm@kvack.org" On 01/13/14 at 06:09pm, Toshi Kani wrote: > On Mon, 2014-01-13 at 16:53 -0800, H. Peter Anvin wrote: > > On 01/13/2014 04:33 PM, Toshi Kani wrote: > > > > > > I do not think it makes sense. You needed memmap=exactmap as a > > > workaround because the kernel did not boot with the firmware's memory > > > info. So, it's broken, and you requested the kernel to ignore the > > > firmware info. > > > > > > Why do you think memory hotplug needs to be supported under such > > > condition, which has to use the broken firmware info? > > > > > > > Even more than memory hotplug: what do we do with NUMA? Since we have > > already told the kernel "the firmware is bogus" it would seem that any > > NUMA optimizations would be a bit ... cantankerous at best, no? > > Agreed that NUMA info can be bogus in this case, but is probably not > critical. > > In majority of the cases, memmap=exactmap is used for kdump and the > firmware info is sane. So, I think we should keep NUMA enabled since it > could be useful when multiple CPUs are enabled for kdump. In Fedora kdump, we by default add numa=off to 2nd kernel cmdline because enabling numa will use a lot more memory, at the same time we have only 128M reserved by default.. Thanks Dave -- 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