linux-kernel - Re: page_to_nid not linked in on PAE

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Message-ID: <alpine.LSU.2.01.1003130132120.24334@obet.zrqbmnf.qr>
Date:	Sat, 13 Mar 2010 01:34:49 +0100 (CET)
From:	Jan Engelhardt <jengelh@...ozas.de>
To:	Andi Kleen <ak@...ux.intel.com>
cc:	Suresh Siddha <suresh.b.siddha@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"hpa@...or.com" <hpa@...or.com>, Nick Piggin <npiggin@...e.de>
Subject: Re: page_to_nid not linked in on PAE


On Friday 2010-03-12 23:33, Andi Kleen wrote:
>
>> Jan, Even with out using the PG_head, PG_tail, PG_uncached and
>> PG_hwpoison, by allowing the NODES_SHIFT to have a maximum value of 9 on
>> 32bit kernel, can still result in the page flags to runout and result in
>> this problem. Best solution for now is to limit the NODES_SHIFT to 5. I
>> don't know of any platforms that have>  32nodes and where we care about
>> 32bit linux kernel. So it should be ok as a fix. If someone in future
>> cares about>  32 nodes for 32bit kernel, then we can think of a better
>> solution. Do you agree? I copied Andi/Nick for their eyes aswell on
>> this.
>
> Seems like the right approach to me. Although it might be better to
> use 1 3 or 1..4 or so, just in case someone else adds more page bits
> later (I'm sure it'll happen again). Even 8 nodes should be plenty for
> 32bit.

Perfectly fine with me. Though I wonder: with SPARSEMEM selected,
I can easily choose the maximum possible value for NODES_SHIFT,
(currently 9, limited imposed by arch/x86/Kconfig).
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