On 08/03/2016 10:18 AM, Baoquan He wrote: > On 08/03/16 at 10:05am, "Zhou, Wenjian/???" 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 <zhouwj-fnst at cn.fujitsu.com> >>>> --- >>>> 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 at lists.infradead.org >>>> http://lists.infradead.org/mailman/listinfo/kexec >>> >>> >> >> >> -- >> Thanks >> Zhou >> >> > > -- Thanks Zhou
