linux-kernel - Re: [rfc][patch 0/3] bootmem2: a memory block-oriented boot time allocator

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Date:	Mon, 05 May 2008 13:23:30 +0200
From:	Johannes Weiner <hannes@...urebad.de>
To:	linux-kernel@...r.kernel.org
Cc:	linux-mm@...ck.org, Ingo Molnar <mingo@...e.hu>,
	Andi Kleen <andi@...stfloor.org>,
	Yinghai Lu <yhlu.kernel@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Yasunori Goto <y-goto@...fujitsu.com>
Subject: Re: [rfc][patch 0/3] bootmem2: a memory block-oriented boot time allocator

Hi,

Johannes Weiner <hannes@...urebad.de> writes:

> The problem is that memory nodes are not anymore garuanteed to be
> linear on certain configurations, they may overlap each other and a
> node might span page ranges that are not physically residing on it.
>
> Note that this is in no way theoretical only, bootmem suffers from
> this fact right now: A pfn range has to be operated on on every node
> that holds it (because a PFN is not unique anymore) and bootmem can
> not garuantee that the memory allocated from a specific node actually
> resides on that node.
>
> For example:
>
> 	node 0: 0-2G, 4-6G
> 	node 1: 2-4G, 6-8G
>
> Bootmem currently sees the 2-4G range twice (and has to operate on
> both node's bitmaps) and if memory is allocated on node 1, it may
> return memory that is between the 2-4G range and actually resides on
> node 0.

Uh, mixup.  The memory resides on node 1 but may get allocated from
node 0.

	Hannes
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