linux-kernel - Re: [PATCH] x86: Allow NR

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Date:	Mon, 04 Nov 2013 09:54:53 -0500
From:	Prarit Bhargava <prarit@...hat.com>
To:	Josh Boyer <jwboyer@...hat.com>
CC:	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Russ Anderson <rja@....com>
Subject: Re: [PATCH] x86: Allow NR_CPUS=1024



On 11/04/2013 09:16 AM, Josh Boyer wrote:
> On Mon, Nov 04, 2013 at 03:10:51PM +0100, Ingo Molnar wrote:
>>
>> * Josh Boyer <jwboyer@...hat.com> wrote:
>>
>>>> Why touch MAXSMP at all? It's really just a shortcut for 'configure 
>>>> the kernel silly large', via a single option, nothing else. You are 
>>>> not forced to use it and it should not affect configurability of 
>>>> NR_CPUS.
>>>>
>>>> What we _really_ want here is to fix NR_CPUS setting: to extend its 
>>>> range and to enforce that NR_CPUS cannot be set larger than 512 
>>>> without setting CONFIG_CPUMASK_OFFSTACK.
>>>
>>> OK.  I was just thinking that if we've come to the conclusion that 4096 
>>> CPUs isn't silly large anymore, we should make MAXSMP be something we 
>>> consider silly large. [...]
>>
>> MAXSMP is also supposed to track the real hardware max as well on x86 - 
>> i.e. we should only increase it to 8192 etc. if such hardware exists.
> 
> Russ, does SGI (or anyone else that you know of) have x86 hardware with
> more than 4096 CPUs?

I can answer this for Russ.  Yes, SGI has boxes that hit 5120.

P.

> 
> If so, I can actually make a bump to the MAXSMP count a separate patch.
> 
> josh
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