Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964863AbbGVA7h (ORCPT ); Tue, 21 Jul 2015 20:59:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35853 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934008AbbGVA7g (ORCPT ); Tue, 21 Jul 2015 20:59:36 -0400 Date: Wed, 22 Jul 2015 08:59:30 +0800 From: Baoquan He To: Yinghai Lu Cc: Dave Young , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Borislav Petkov , Andrew Morton , Jiri Kosina , Vivek Goyal , Linux Kernel Mailing List Subject: Re: [PATCH v2] Do not reserve crashkernel high memory if crashkernel low memory reserving failed Message-ID: <20150722005930.GE1834@dhcp-17-102.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> <20150721075011.GC16747@dhcp-128-28.nay.redhat.com> <20150721082343.GC30649@dhcp-129-220.nay.redhat.com> <20150721085846.GA23020@dhcp-128-28.nay.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1112 Lines: 35 On 07/21/15 at 12:22pm, Yinghai Lu wrote: > On Tue, Jul 21, 2015 at 1:58 AM, Baoquan He wrote: > > > Maybe system which don't need low memory is rare, only for testing? > > No, it is not rare. > > All recent intel based systems with iommu support does not need low. Yeah, you are right. > > And those systems get punished by following patch: > > | commit 94fb9334182284e8e7e4bcb9125c25dc33af19d4 > | Author: Joerg Roedel > | Date: Wed Jun 10 17:49:42 2015 +0200 > | > | x86/crash: Allocate enough low memory when crashkernel=high > > that reserve 256M low always. and those 256M get wasted. > > That commit should only be used to workaround some systems that > have partial iommu support. Those big servers mostly has hardware iommu. But they still can enable swiotlb suport. Then low memory is needed. > > 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/