linux-kernel - Re: [PATCH -v2 5/5] x86: use dmi check to treat disabled cpus as hotplug cpus.

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Message-ID: <4B4E511C.1050609@kernel.org>
Date:	Wed, 13 Jan 2010 15:02:52 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
CC:	"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <andi@...stfloor.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"ananth@...ibm.com" <ananth@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v2 5/5] x86: use dmi check to treat disabled cpus as
 hotplug cpus.

On 01/13/2010 02:49 PM, Suresh Siddha wrote:
> On Wed, 2010-01-13 at 14:36 -0800, H. Peter Anvin wrote:
>> On 01/13/2010 02:29 PM, Suresh Siddha wrote:
>>>>
>>>> Well, that *is* working around broken code, in this case the broken code
>>>> is the percpu allocation strategy.
>>>
>>> Andi, Recently percpu folks changed the per-cpu static first chunk to
>>> PMD SIZE right. I think that is what causing all this issue.
>>>
>>
>> Please don't tell me we're allocating 2 MB per CPU and throwing away
>> most of it...
> 
> Looking at the percpu code, they do seem to free the unused memory in
> that hole.
> 
> Yinghai, what are the configurations that need MB's of per cpu area?

please check attached...

YH

View attachment "config.fullx" of type "text/plain" (73257 bytes)