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

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Message-Id: <1263421753.2865.103.camel@sbs-t61.sc.intel.com>
Date:	Wed, 13 Jan 2010 14:29:13 -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 14:27 -0800, H. Peter Anvin wrote:
> On 01/13/2010 02:23 PM, Andi Kleen wrote:
> >> There are configurations in which percpu memory is in the megabytes.
> > 
> > There used to be some like this (with some broken debug code), but they
> > got all fixed i believe to only allocate on real cpu hotplug. 
> > 
> > If not the right way is to fix them, not add DMI blacklists.
> > 
> > Beside when you enable debug code you probably don't care about 
> > a few MB too much.
> > 
> >> This is exactly why we need high water mark allocation of percpu memory:
> > 
> > No we just need to fix any percpu pigs (if there are really any left,
> > I did a couple of patches some time ago)
> > 
> > "Don't work around broken code -- fix it"
> > 
> 
> 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.

thanks,
suresh

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