From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f41.google.com (mail-pa0-f41.google.com [209.85.220.41]) by kanga.kvack.org (Postfix) with ESMTP id 963D56B0036 for ; Mon, 13 Jan 2014 20:53:38 -0500 (EST) Received: by mail-pa0-f41.google.com with SMTP id fb1so6819739pad.14 for ; Mon, 13 Jan 2014 17:53:38 -0800 (PST) Received: from g1t0029.austin.hp.com (g1t0029.austin.hp.com. [15.216.28.36]) by mx.google.com with ESMTPS id n8si17282657pax.305.2014.01.13.17.53.36 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Mon, 13 Jan 2014 17:53:37 -0800 (PST) Message-ID: <1389664055.1792.269.camel@misato.fc.hp.com> Subject: Re: [PATCH 2/2] x86, e820 disable ACPI Memory Hotplug if memory mapping is specified by user [v2] From: Toshi Kani Date: Mon, 13 Jan 2014 18:47:35 -0700 In-Reply-To: <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> <20140114015202.GD4327@dhcp-16-126.nay.redhat.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dave Young 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 Tue, 2014-01-14 at 09:52 +0800, Dave Young wrote: > 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.. That quite makes sense as we only enable a single CPU today. Thanks, -Toshi -- 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