[PATCH v3 1/2] Documentation: kdump: remind user of nr_cpus

[PATCH v3 1/2] Documentation: kdump: remind user of nr_cpus

[Zhou Wenjian]

v2->v3: add description of nr_cpus.
v1->v2: change nr_cpus to maxcpus

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

Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.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..4aa194e 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, we 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 v3 2/2] Documentation: kdump: add description of bringing up SMP dump-capture kernel

[Zhou Wenjian]

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@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
+  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

Re: [PATCH v3 1/2] Documentation: kdump: remind user of nr_cpus

[Baoquan He]

On 08/03/16 at 08:59am, Zhou Wenjian wrote:
> v2->v3: add description of nr_cpus.
> v1->v2: change nr_cpus to maxcpus
> 
> nr_cpus can help to save memory. So we should remind user of it.
> 
> Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.com>
> ---
>  Documentation/kdump/kdump.txt | 2 ++
>  1 file changed, 2 insertions(+)

Looks good to me! Thanks, Wenjian.

Ack this series
Acked-by: Baoquan He <bhe@redhat.com>


Hi Andrew,

Could you please help merge this patchset?

Thanks
Baoquan

> 
> diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
> index 88ff63d..4aa194e 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, we 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 v3 2/2] Documentation: kdump: add description of bringing up SMP dump-capture kernel

[Baoquan He]

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@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.

> +  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

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

["Zhou, Wenjian/周文剑"]

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@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.

>> +  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

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

[Baoquan He]

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 <zhouwj-fnst@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.

> 
> >>+  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
> 
> 

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

["Zhou, Wenjian/周文剑"]

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 <zhouwj-fnst@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@lists.infradead.org
>>>> http://lists.infradead.org/mailman/listinfo/kexec
>>>
>>>
>>
>>
>> --
>> Thanks
>> Zhou
>>
>>
>
>


-- 
Thanks
Zhou

Re: [PATCH v3 1/2] Documentation: kdump: remind user of nr_cpus

[Dave Young]

On 08/03/16 at 08:59am, Zhou Wenjian wrote:
> v2->v3: add description of nr_cpus.
> v1->v2: change nr_cpus to maxcpus
> 
> nr_cpus can help to save memory. So we should remind user of it.
> 
> Signed-off-by: Zhou Wenjian <zhouwj-fnst@cn.fujitsu.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..4aa194e 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, we should replace it by nr_cpus to
> +  save memory if supported by the current ARCH, such as x86. 

Can you replace "we" with "you" in both these patches?

Thanks
Dave