[PATCH v8 0/2] update the doc of kdump

[PATCH v8 0/2] update the doc of kdump

[Zhou Wenjian]

v7->v8: fix "a SMP kernel" to "an SMP kernel" and replace "\" with "/"
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 v8 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>
Acked-by: Xunlei Pang <xpang@redhat.com>
---
 Documentation/kdump/kdump.txt | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
index 88ff63d..e8da1d5 100644
--- a/Documentation/kdump/kdump.txt
+++ b/Documentation/kdump/kdump.txt
@@ -390,9 +390,11 @@ Notes on loading the dump-capture kernel:
 * Boot parameter "1" boots the dump-capture kernel into single-user
   mode without networking. If you want networking, use "3".
 
-* We generally don' have to bring up a SMP kernel just to capture the
+* We generally don' have to bring up an 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

Re: [PATCH v8 1/2] Documentation: kdump: remind user of nr_cpus

[Joe Perches]

On Thu, 2016-08-18 at 10:31 +0800, Zhou Wenjian wrote:
> nr_cpus can help to save memory. So we should remind user of it.

trivia:
> diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
[]
> @@ -390,9 +390,11 @@ Notes on loading the dump-capture kernel:
>  * Boot parameter "1" boots the dump-capture kernel into single-user
>    mode without networking. If you want networking, use "3".
>  
> -* We generally don' have to bring up a SMP kernel just to capture the
> +* We generally don' have to bring up an SMP kernel just to capture the

don't or do not

Re: [PATCH v8 1/2] Documentation: kdump: remind user of nr_cpus

[Dave Young]

On 08/17/16 at 07:36pm, Joe Perches wrote:
> On Thu, 2016-08-18 at 10:31 +0800, Zhou Wenjian wrote:
> > nr_cpus can help to save memory. So we should remind user of it.
> 
> trivia:
> > diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
> []
> > @@ -390,9 +390,11 @@ Notes on loading the dump-capture kernel:
> >  * Boot parameter "1" boots the dump-capture kernel into single-user
> >    mode without networking. If you want networking, use "3".
> >  
> > -* We generally don' have to bring up a SMP kernel just to capture the
> > +* We generally don' have to bring up an SMP kernel just to capture the
> 
> don't or do not
> 

Use do not is better, also need replace 'We' with 'You' to be
consistent with other part.

Re: [PATCH v8 1/2] Documentation: kdump: remind user of nr_cpus

["Zhou, Wenjian/周文剑"]

On 08/18/2016 02:47 PM, Dave Young wrote:
> On 08/17/16 at 07:36pm, Joe Perches wrote:
>> On Thu, 2016-08-18 at 10:31 +0800, Zhou Wenjian wrote:
>>> nr_cpus can help to save memory. So we should remind user of it.
>>
>> trivia:
>>> diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
>> []
>>> @@ -390,9 +390,11 @@ Notes on loading the dump-capture kernel:
>>>   * Boot parameter "1" boots the dump-capture kernel into single-user
>>>     mode without networking. If you want networking, use "3".
>>>
>>> -* We generally don' have to bring up a SMP kernel just to capture the
>>> +* We generally don' have to bring up an SMP kernel just to capture the
>>
>> don't or do not
>>
>
> Use do not is better, also need replace 'We' with 'You' to be
> consistent with other part.
>
>

I think it's better to fix it in another patch,
for it doesn't have much relevance to the patch set.
I'll post it alone later.

-- 
Thanks
Zhou

[PATCH v8 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>
Acked-by: Xunlei Pang <xpang@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 e8da1d5..c781d49 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 an
+  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