[PATCH v7 0/2] update the doc of kdump

[PATCH v7 0/2] update the doc of kdump

[Zhou Wenjian]

v6->v7: fix typo
v5->v6: replace "we" with "you"
v4->v5: move change log to cover letter
v3->v4: update the description of bring up SMP dump-capture kernel
v2->v3: add description of nr_cpus.
v1->v2: change nr_cpus to maxcpus


Zhou Wenjian (2):
  Documentation: kdump: remind user of nr_cpus
  Documentation: kdump: add description of enable multi-cpus support

 Documentation/kdump/kdump.txt | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

-- 
1.8.3.1

[PATCH v7 1/2] Documentation: kdump: remind user of nr_cpus

[Zhou Wenjian]

nr_cpus can help to save memory. So we should remind user of it.

Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>
Acked-by: Baoquan He <bhe@redhat.com>
---
 Documentation/kdump/kdump.txt | 2 +++-
 1 file changed, 2 insertions(+)

diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
index 88ff63d..96da2b7 100644
--- a/Documentation/kdump/kdump.txt
+++ b/Documentation/kdump/kdump.txt
@@ -393,6 +393,8 @@ Notes on loading the dump-capture kernel:
 * 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.
+  Note, though maxcpus always works, you should replace it by nr_cpus to
+  save memory if supported by the current ARCH, such as x86.
 
 * 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
-- 
1.8.3.1

[PATCH v7 2/2] Documentation: kdump: add description of enable multi-cpus support

[Zhou Wenjian]

multi-cpu support is useful to improve the performance of kdump in
some cases. So add the description of enable multi-cpu support in
dump-capture kernel.

Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>
Acked-by: Baoquan He <bhe@redhat.com>
---
 Documentation/kdump/kdump.txt | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
index 96da2b7..c93a6e0 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, you should replace it by nr_cpus to
   save memory if supported by the current ARCH, such as x86.
 
+* You should enable multi-cpu support in dump-capture kernel if you intend
+  to use multi-thread programs with it, such as parallel dump feature of
+  makedumpfile. Otherwise, the multi-thread program may have a great
+  performance degradation. To enable multi-cpu support, you should bring up
+  a SMP dump-capture kernel and specify maxcpus\nr_cpus, disable_cpu_apicid=[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

Re: [PATCH v7 2/2] Documentation: kdump: add description of enable multi-cpus support

[Xunlei Pang]

On 2016/08/18 at 09:50, Zhou Wenjian wrote:
> multi-cpu support is useful to improve the performance of kdump in
> some cases. So add the description of enable multi-cpu support in
> dump-capture kernel.
>
> Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>
> Acked-by: Baoquan He <bhe@redhat.com>
> ---
>  Documentation/kdump/kdump.txt | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
> index 96da2b7..c93a6e0 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, you should replace it by nr_cpus to
>    save memory if supported by the current ARCH, such as x86.
>  
> +* You should enable multi-cpu support in dump-capture kernel if you intend
> +  to use multi-thread programs with it, such as parallel dump feature of
> +  makedumpfile. Otherwise, the multi-thread program may have a great
> +  performance degradation. To enable multi-cpu support, you should bring up
> +  a SMP dump-capture kernel and specify maxcpus\nr_cpus, disable_cpu_apicid=[X]

s/a SMP/an SMP/
For "maxcpus\nr_cpus", I think to use slash instead of backslash in Linux is better.

Otherwise, looks good to me.

Regards,
Xunlei

> +  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