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

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Date:	Wed, 13 Jan 2010 14:49:18 -0800
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andi Kleen <andi@...stfloor.org>, Yinghai Lu <yinghai@...nel.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 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?

thanks,
suresh

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