From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754542AbZHYGhy (ORCPT ); Tue, 25 Aug 2009 02:37:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753136AbZHYGhw (ORCPT ); Tue, 25 Aug 2009 02:37:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33876 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753029AbZHYGhv (ORCPT ); Tue, 25 Aug 2009 02:37:51 -0400 Message-ID: <4A938698.40302@redhat.com> Date: Tue, 25 Aug 2009 14:37:12 +0800 From: Amerigo Wang User-Agent: Thunderbird 2.0.0.22 (X11/20090719) MIME-Version: 1.0 To: mohan@in.ibm.com CC: Michael Ellerman , linux-kernel@vger.kernel.org, tony.luck@intel.com, linux-ia64@vger.kernel.org, Neil Horman , "Eric W. Biederman" , kamezawa.hiroyu@jp.fujitsu.com, Andi Kleen , akpm@linux-foundation.org, bernhard.walle@gmx.de, Fenghua Yu , Ingo Molnar , Anton Vorontsov Subject: Re: [Patch 6/8] powerpc: add CONFIG_KEXEC_AUTO_RESERVE References: <20090821065637.4855.32234.sendpatchset@localhost.localdomain> <20090821065739.4855.19179.sendpatchset@localhost.localdomain> <1251121443.10645.56.camel@concordia> <20090824144542.GB11956@in.ibm.com> In-Reply-To: <20090824144542.GB11956@in.ibm.com> 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 M. Mohan Kumar wrote: > On Mon, Aug 24, 2009 at 11:44:03PM +1000, Michael Ellerman wrote: > >> On Fri, 2009-08-21 at 02:55 -0400, Amerigo Wang wrote: >> >>> Introduce a new config option KEXEC_AUTO_RESERVE for powerpc. >>> >>> Index: linux-2.6/arch/powerpc/Kconfig >>> =================================================================== >>> --- linux-2.6.orig/arch/powerpc/Kconfig >>> +++ linux-2.6/arch/powerpc/Kconfig >>> @@ -346,6 +346,17 @@ config KEXEC >>> support. As of this writing the exact hardware interface is >>> strongly in flux, so no good recommendation can be made. >>> >>> +config KEXEC_AUTO_RESERVE >>> + bool "automatically reserve memory for kexec kernel" >>> + depends on KEXEC >>> + default y >>> + ---help--- >>> + Automatically reserve memory for a kexec kernel, so that you don't >>> + need to specify numbers for the "crashkernel=X@Y" boot option, >>> + instead you can use "crashkernel=auto". To make this work, you need >>> + to have more than 4G memory. On PPC, 256M is reserved, 1/32 memory >>> + on PPC64, but it will not exceed 1T/32. >>> >> That aside, I don't see how this will be useful in practice, if it only >> works for memory sizes over 4G? Or are we saying that people with less >> than 4G don't need crash kernels? If we're not saying that, those users, >> or those users' distros, still need to do some logic to work out if they >> have < 4GB of memory and if so pick a crash kernel size. So why can't >> they pick the size in the > 4GB case also? >> > > True, I wanted to test the patch and when tested on a ppc64 machine which > has RAM less than 4GB, I have to modify arch_default_crash_size routine to > return 256MB (I didn't have a PPC64 machine with more than 4GB RAM handy). > So its better to consider machines with less than 4GB RAM also. > OK, how about 2G on ppc? Is it safe to reserve 256M when I have 2G? > PPC64 crashkernel base is always 32MB. So at least ppc64 code should have > its own arch_default_crash_base to return 32MB to avoid the kernel warning > message "Crash kernel location must be 0x2000000" > Hmm, good point, how about KDUMP_KERNELBASE? It looks fine for both ppc and ppc64. Thanks!