Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753354AbbGUITr (ORCPT ); Tue, 21 Jul 2015 04:19:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59453 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753193AbbGUITp (ORCPT ); Tue, 21 Jul 2015 04:19:45 -0400 Date: Tue, 21 Jul 2015 16:19:32 +0800 From: Dave Young To: Ingo Molnar Cc: Baoquan He , tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, bp@suse.de, akpm@linux-foundation.org, jkosina@suse.cz, vgoyal@redhat.com, linux-kernel@vger.kernel.org, yinghai@kernel.org, Peter Zijlstra Subject: Re: [PATCH v2] Do not reserve crashkernel high memory if crashkernel low memory reserving failed Message-ID: <20150721081932.GB30649@dhcp-129-220.nay.redhat.com> References: <1437304064-9916-1-git-send-email-bhe@redhat.com> <20150719145320.GB9968@dhcp-17-102.nay.redhat.com> <20150721073123.GA30649@dhcp-129-220.nay.redhat.com> <20150721073814.GA17513@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150721073814.GA17513@gmail.com> User-Agent: Mutt/1.5.22.1-rc1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2222 Lines: 69 On 07/21/15 at 09:38am, Ingo Molnar wrote: > > * Dave Young wrote: > > > Hi, Baoquan > > > > The interface was introduced by Yinghai, ccing him. > > Also, why was this syntax introduced in the first place? Why should the user > care?? The history is like below, I might miss something, Yinghai/HPA/Vivek may correct and provide more background: First commit is below: commit 7d41a8a4a2b2438621a9159477bff36a11d79a42 Author: Yinghai Lu Date: Thu Jan 24 12:20:10 2013 -0800 x86, kdump: Remove crashkernel range find limit for 64bit Previously kdump reservation is limited to <896M, above commit remove the limitation. Then because of kdump kernel need access low mem for swiotlb buffer, thus there's commit below: commit 0212f9159694be61c6bc52e925fa76643e0c1abf Author: Yinghai Lu Date: Thu Jan 24 12:20:11 2013 -0800 x86: Add Crash kernel low reservation Later, Vivek found old kexec-tools does not work, then Yinghai introduced new param crashkernel_high=: commit 55a20ee7804ab64ac90bcdd4e2868a42829e2784 Author: Yinghai Lu Date: Mon Apr 15 22:23:47 2013 -0700 x86, kdump: Retore crashkernel= to allocate under 896M Finally it becomes crashkernel=x,high: commit adbc742bf78695bb98c79d18c558b61571748b99 Author: Yinghai Lu Date: Mon Apr 15 22:23:48 2013 -0700 x86, kdump: Change crashkernel_high/low= to crashkernel=,high/low > > We should only have a single crashkernel option, to enable it - and everything > else should be figured out by the kernel, automatically. Presonally I do not current complicated params either, I hope we can have an elegant interface, but seems there's no better way to resolve the low memory only requirement for software tlb. > > Any other sub-options just paper over some fragility elsewhere and make the > feature harder to use, hence more fragile. Agree, it is becoming worse.. Thanks Dave -- 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/