linux-kernel - Re: [PATCH v9 1/2] Documentation: kdump: remind user of nr

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Date:   Fri, 19 Aug 2016 08:33:21 +0800
From:   "Zhou, Wenjian/周文剑" 
        <zhouwj-fnst@...fujitsu.com>
To:     Jonathan Corbet <corbet@....net>
CC:     <linux-kernel@...r.kernel.org>, <akpm@...ux-foundation.org>,
        <dyoung@...hat.com>, <bhe@...hat.com>, <vgoyal@...hat.com>,
        <kexec@...ts.infradead.org>, <linux-doc@...r.kernel.org>,
        <xlpang@...hat.com>, <joe@...ches.com>
Subject: Re: [PATCH v9 1/2] Documentation: kdump: remind user of nr_cpus

Hi Jonathan,

Thanks for your reply.

On 08/19/2016 01:18 AM, Jonathan Corbet wrote:
> On Thu, 18 Aug 2016 11:11:46 +0800
> Zhou Wenjian <zhouwj-fnst@...fujitsu.com> wrote:
>
> Thank you for working to improve the documentation!
>
>>   * 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.
>
> So, IMHO, this seems like the wrong place for this.  I've just spent a bit
> of time staring at kernel-parameters.txt, and there is no way for a
> clueless user like me to know what the difference is between maxcpus= and
> nr_cpus= would be.  A far better patch would be to update the
> documentation there to make that clear.  Any chance you would be willing
> to do that?
>
> Then, rather than tacking an "ignore what you just read" note into
> kdump.txt, it could maybe be rewritten to simply say what users should do?
>

I was also confused by maxcpus and nr_cpus before writing this patch.
I think it is a good choice to describe it in kernel-parameters.txt.

Then, only two things need to be done I think.
One is move the above description to maxcpus= in kernel-parameters.txt.
And the other is replace maxcpus with maxcpus/nr_cpus in kdump.txt.

How do you think?

-- 
Thanks
Zhou