Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754371Ab3CKS6M (ORCPT ); Mon, 11 Mar 2013 14:58:12 -0400 Received: from terminus.zytor.com ([198.137.202.10]:44839 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753491Ab3CKS6K (ORCPT ); Mon, 11 Mar 2013 14:58:10 -0400 Message-ID: <513E28B8.3000502@zytor.com> Date: Mon, 11 Mar 2013 11:55:52 -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: Yinghai Lu CC: Vivek Goyal , 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> In-Reply-To: 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: 1305 Lines: 35 On 03/11/2013 11:50 AM, Yinghai Lu 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...? > > We did not touch 32 bit system. > > Do you mean that we should > For 64bit, we should try under 4G, and then try MAXMEM > instead of try under 896M, then 4G, and MAXMEM? > > Try 896M at first, we will let user to avoid updating their kexec-tools. > Are you saying 896M is somehow hardcoded into kexec-tools? I actually disagree with trying low memory at all. Push kdump as high into the memory range as we can go, if there is a performance penalty it is much better to take it in the kdump kernel. All the voodoo to try to keep people from updating kexec-tools is disturbing; although breaking userspace is bad, updating kexec-tools is probably easier than updating the kernel, and carrying the voodoo on indefinitely has serious consequences. -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/