From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757444AbcHCCSl (ORCPT ); Tue, 2 Aug 2016 22:18:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56368 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752988AbcHCCSd (ORCPT ); Tue, 2 Aug 2016 22:18:33 -0400 Date: Wed, 3 Aug 2016 10:18:25 +0800 From: Baoquan He To: =?utf-8?B?Ilpob3UsIFdlbmppYW4v5ZGo5paH5YmRIg==?= Cc: linux-kernel@vger.kernel.org, dyoung@redhat.com, d.hatayama@jp.fujitsu.com, kexec@lists.infradead.org Subject: Re: [PATCH v3 2/2] Documentation: kdump: add description of bringing up SMP dump-capture kernel Message-ID: <20160803021825.GB3637@x1.redhat.com> References: <1470185952-23477-1-git-send-email-zhouwj-fnst@cn.fujitsu.com> <1470185952-23477-2-git-send-email-zhouwj-fnst@cn.fujitsu.com> <20160803015818.GB2465@x1.redhat.com> <57A15156.3060507@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <57A15156.3060507@cn.fujitsu.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Wed, 03 Aug 2016 02:18:32 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/03/16 at 10:05am, "Zhou, Wenjian/周文剑" wrote: > On 08/03/2016 09:58 AM, Baoquan He wrote: > >On 08/03/16 at 08:59am, Zhou Wenjian wrote: > >>SMP dump-capture kernel is useful to improve the performance of kdump in > >>some cases. So add the description of bringing up SMP dump-capture kernel. > >> > >>Signed-off-by: Zhou Wenjian > >>--- > >> Documentation/kdump/kdump.txt | 7 +++++++ > >> 1 file changed, 7 insertions(+) > >> > >>diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt > >>index 4aa194e..948b42d 100644 > >>--- a/Documentation/kdump/kdump.txt > >>+++ b/Documentation/kdump/kdump.txt > >>@@ -396,6 +396,13 @@ Notes on loading the dump-capture kernel: > >> Note, though maxcpus always works, we should replace it by nr_cpus to > >> save memory if supported by the current ARCH, such as x86. > >> > >>+* We should bring up a SMP dump-capture kernel if we intend to use > > > >Well, here about SMP dump-capture kernel do you mean kdump kernel with > >multi-cpu? If I understand it correctly, it's still SMP kdump kernel > >though nr_cpus=1 is specified. > > > > Actually, I haven't know the detail about it. I wrote the sentence almost > based on the original description: > > * We generally don' have to bring up a SMP kernel just to capture the > dump. Hence generally it is useful either to build a UP dump-capture > kernel or specify maxcpus=1 option while loading dump-capture kernel. This is right. Here it means either you build a UP kernel used for kdump kernel because kdump kernel doesn't have to be the same as the 1st kernel, or you use smp kernel with maxcpus=1 specified. So if you want to say kdump kernel with multi-cpu need be brought up to improve the performance of parallel dumping, you need point it out clearly. > > >>+ multi-threads programs with it, such as parallel dump feature of > >>+ makedumpfile. Otherwise, the multi-threads program may have a great > >>+ performance degradation. To bring up a SMP dump-capture kernel, we > >>+ should specify maxcpus\nr_cpus and disable_cpu_apic=[X] options while > >>+ loading it. > >>+ > >> * For s390x there are two kdump modes: If a ELF header is specified with > >> the elfcorehdr= kernel parameter, it is used by the kdump kernel as it > >> is done on all other architectures. If no elfcorehdr= kernel parameter is > >>-- > >>1.8.3.1 > >> > >> > >> > >> > >>_______________________________________________ > >>kexec mailing list > >>kexec@lists.infradead.org > >>http://lists.infradead.org/mailman/listinfo/kexec > > > > > > > -- > Thanks > Zhou > >