Re: [PATCH v3 2/2] Documentation: kdump: add description of bringing up SMP dump-capture kernel

["Zhou, Wenjian/åæå"]

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@xxxxxxxxxxxxxx>
> > ---
> >   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.

> > +  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
> >
> >
> >
> >
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--
Thanks
Zhou