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

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Date:   Mon, 22 Aug 2016 09:14:08 +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

On 08/19/2016 11:57 PM, Jonathan Corbet wrote:
> On Fri, 19 Aug 2016 08:33:21 +0800
> "Zhou, Wenjian/周文剑" <zhouwj-fnst@...fujitsu.com> wrote:
>
>> 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?
>
> That is not quite what I had in mind, sorry.  What I would really like to
> see in kernel-parameters.txt is an explanation of how those two parameters
> differ - what do they do differently and how should a user choose one over
> the other?  What we have now offers no guidance in that matter.
>

I thought about it. I think user may not need this.
What user really want to know is how to choose.
And it is also not a hard work. If nr_cpus is not supported by the ARCH, use maxcpus.
Otherwise, nr_cpus. The reason why maxcpus still exists is nr_cpus can't be supported
by some ARCHes.

I think it may be why the author didn't write too much description of it.

> I suspect that may be a bit more than you had signed up to do.  As an
> intermediate step, how about this: rather than tacking on those lines in
> kdump.txt, rewrite that paragraph to simply say what the reader should
> use.  If nr_cpus is good for everybody, just say that, but your previous
> patch suggests that the situation isn't quite that simple?
>

Actually, if nr_cpus always usable, there won't be these discussions.


-- 
Thanks
Zhou