From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754354AbZHaDZb (ORCPT ); Sun, 30 Aug 2009 23:25:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754303AbZHaDZb (ORCPT ); Sun, 30 Aug 2009 23:25:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:3996 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754253AbZHaDZa (ORCPT ); Sun, 30 Aug 2009 23:25:30 -0400 Message-ID: <4A9B4294.6080902@redhat.com> Date: Mon, 31 Aug 2009 11:25:08 +0800 From: Amerigo Wang User-Agent: Thunderbird 2.0.0.22 (X11/20090719) MIME-Version: 1.0 To: "Eric W. Biederman" CC: michael@ellerman.id.au, linux-kernel@vger.kernel.org, tony.luck@intel.com, linux-ia64@vger.kernel.org, Neil Horman , kamezawa.hiroyu@jp.fujitsu.com, Andi Kleen , "M. Mohan Kumar" , akpm@linux-foundation.org, bernhard.walle@gmx.de, Fenghua Yu , Ingo Molnar , Anton Vorontsov Subject: Re: [Patch 0/8] V5 Implement crashkernel=auto References: <20090827031800.4534.94868.sendpatchset@localhost.localdomain> <1251680096.5279.6.camel@concordia> In-Reply-To: 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 Eric W. Biederman wrote: > Michael Ellerman writes: > > >> On Wed, 2009-08-26 at 23:15 -0400, Amerigo Wang wrote: >> >>> V4 -> V5: >>> - Rename the global functions, as suggested by Andrew. >>> - Save some macros, as suggested by Andrew. >>> - Change the high threshold, from 32G to 4G. >>> - Change the low threshold on ppc, suggested by ppc developers. >>> - Make the mm part as a seperate function, suggest by Eric. >>> - Make the IA64 code more readable. >>> - Reorder the patchset again, since review from mm people is done. >>> >>> V3 -> V4: >>> - Reorder the patches. >>> - Really free the reserved memory, instead of remapping it. >>> (Thanks to KAMEZAWA Hiroyuki!) >>> - Release the reserved memory resource when the size is 0. >>> - Use strict_strtoul() instead of simple_strtoul(). >>> >>> V2 -> V3: >>> - Use more clever way to calculate reserved memory size, especially for IA64. >>> - Add that patch that implements shrinking reserved memory >>> >>> V1 -> V2: >>> - Use include/asm-generic/kexec.h, suggested by Neil. >>> - Rename a local variable, suggested by Fenghua. >>> - Fix some style problems found by checkpatch.pl. >>> - Unify the Kconfig docs. >>> >>> This series of patch implements automatically reserved memory for crashkernel, >>> by introducing a new boot option "crashkernel=auto". This idea is from Neil. >>> >>> In case of breaking user-space applications, it modifies this boot option after >>> it decides how much memory should be reserved. >>> >>> On different arch, the threshold and reserved memory size is different. Please >>> refer patch 7/8 which contains an update for the documentation. >>> >>> Patch 8/8 implements shrinking reserved memory at run-time, which is useful >>> when more than enough memory is reserved automatically. >>> >>> This patchset _is_ already tested on x86_64, IA64 and ppc64. >>> >> I don't want to sound like a micro-kernel zealot, I'm not, but I'm still >> unconvinced as to why the auto logic needs to go in the kernel. What is >> the compelling reason that the kernel needs to do this calculation vs >> some userspace tool? We already have the syntax that allows defining a >> different crash size depending on the size of RAM. >> >> The shrinking of reserved memory is cool. >> > > Michael I am in agreement with you. > The shrinking is good. > > If we can come up with some simple and generic logic that we can use > to reserve memory then I am in favor. However all this patchset is > doing is moving user space specific arbitrary hacks into the kernel we > do that perfectly well on the command line. Having the amount to > reserve be arch specific is complete non-sense and a major maintenance > pain. > Ok, since you guys think we should not do sth in kernel space if we can do it in user space, why not removing the extended crash kernel syntax?? E.g. crashkernel=512M-2G:64M,2G-:128M I am *quite* sure this can be done in user space too. In theory, only you need is just: crashkernel=X@Y all the rest things can be done in user space. Enjoy!