Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965000AbbFJRsW (ORCPT ); Wed, 10 Jun 2015 13:48:22 -0400 Received: from mail-ig0-f172.google.com ([209.85.213.172]:36553 "EHLO mail-ig0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964996AbbFJRsP (ORCPT ); Wed, 10 Jun 2015 13:48:15 -0400 MIME-Version: 1.0 In-Reply-To: <20150610070412.GA16351@dhcp-128-28.nay.redhat.com> References: <1433749795-5796-1-git-send-email-bp@alien8.de> <1433749795-5796-4-git-send-email-bp@alien8.de> <20150610070412.GA16351@dhcp-128-28.nay.redhat.com> Date: Wed, 10 Jun 2015 10:48:14 -0700 X-Google-Sender-Auth: Qon5eZXrABFKHhwXUMfyfewoxe0 Message-ID: Subject: Re: [PATCH 3/3] x86/crash: Allocate enough low memory when crashkernel=high From: Yinghai Lu To: Baoquan He , Joerg Roedel Cc: Borislav Petkov , Ingo Molnar , LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1528 Lines: 34 On Wed, Jun 10, 2015 at 12:04 AM, Baoquan He wrote: > > In fact in this case, it doesn't matter how much memory the system has > since most of them is above 4G and only 72M is reserved for dma/swiotlb > in kdump kernel. And it doesn't matter much how many pci/pcie cards the > system has since it matters how greedy those devices expects dma > allocation. > > Before Joerg posted this patchset v1, our customer complained about > this too. That means this is not individual case. I think it makes sense > to increase the default low-memory to make kdump succeed, it's > definitely better than letting user get a failed kdump and then know > they need specify more low-memory manually. If user clearly know their > system doesn't need so much low-memory, specifying crashkernel=xx,low > works for them. Now intel 4socket or 8socket system mostly have [2G,4G) for mmio low. also I saw one system had [1.5G, 4G) for mmio. So under 4G low ram is tight, with changing default to 256M is just lazy and punishing the other system that does not need that. those systems do not need to have "crashkernel=xx,low" before. should have other smart way to detect and update the default value. even dmi blacklist way is better than just changing default value. Thanks Yinghai -- 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/