From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757210AbcHCCVB (ORCPT ); Tue, 2 Aug 2016 22:21:01 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:26522 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752988AbcHCCUv (ORCPT ); Tue, 2 Aug 2016 22:20:51 -0400 X-IronPort-AV: E=Sophos;i="5.22,518,1449504000"; d="scan'208";a="9457158" Message-ID: <57A154B7.4090407@cn.fujitsu.com> Date: Wed, 3 Aug 2016 10:19:35 +0800 From: =?UTF-8?B?Ilpob3UsIFdlbmppYW4v5ZGo5paH5YmRIg==?= User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Baoquan He CC: , , , Subject: Re: [PATCH v3 2/2] Documentation: kdump: add description of bringing up SMP dump-capture kernel 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> <20160803021825.GB3637@x1.redhat.com> In-Reply-To: <20160803021825.GB3637@x1.redhat.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-yoursite-MailScanner-ID: 7C4DF42CA543.AA560 X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: zhouwj-fnst@cn.fujitsu.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/03/2016 10:18 AM, Baoquan He wrote: > 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. > I see. I will update the patch. >> >>>> + 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 >> >> > > -- Thanks Zhou