Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754408Ab3CKTHR (ORCPT ); Mon, 11 Mar 2013 15:07:17 -0400 Received: from terminus.zytor.com ([198.137.202.10]:45082 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751636Ab3CKTHP (ORCPT ); Mon, 11 Mar 2013 15:07:15 -0400 Message-ID: <513E2AC6.1000707@zytor.com> Date: Mon, 11 Mar 2013 12:04:38 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130219 Thunderbird/17.0.3 MIME-Version: 1.0 To: Vivek Goyal CC: Yinghai Lu , Thomas Gleixner , Ingo Molnar , WANG Chao , "Eric W. Biederman" , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86, kdump: Set crashkernel_low automatically References: <513D52BA.3070206@redhat.com> <1362977817-23297-1-git-send-email-yinghai@kernel.org> <20130311144853.GB8482@redhat.com> <20130311150256.GC8482@redhat.com> <20130311182655.GB12107@redhat.com> <513E2695.3080707@zytor.com> <20130311190242.GC12107@redhat.com> In-Reply-To: <20130311190242.GC12107@redhat.com> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1300 Lines: 31 On 03/11/2013 12:02 PM, Vivek Goyal wrote: >> >> What is the purpose of reserving that kind of memory below 896 MB? If >> you have a 32-bit system, it will likely be useless since you are >> robbing the primary of most of lowmem, on a 64-bit system 896 MB is not >> a magic value in any way...? > > Actually I am not sure where did 896MB magic value had come from for > x86_64 so far. I assumed that it was some kexec-tools limitation so > first trying 896MB will preserve working with old kexec-tools. If it > was some kernel limitation, then I agree it should not be required anymore. > > I do remember that old pugatory had 2G limit. So may be we can first > try reserve with-in first 2G, then with-in first 4G and then above > 4G. (Assuming 896M was not kexec-tools limitation and had something > to do with kernel/initramfs). > It is obvious where it *originated* from... it is the *default* (but not necessarily the actual!) HIGHMEM crossover point on x86-32. Whether this limitation has crept into somewhere else is a good question. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/