linux-kernel - Re: [PATCH 0/3] bootmem2 III

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Message-ID: <48275493.40601@firstfloor.org>
Date:	Sun, 11 May 2008 22:18:27 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Johannes Weiner <hannes@...urebad.de>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Ingo Molnar <mingo@...e.hu>,
	Yinghai Lu <yhlu.kernel@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 0/3] bootmem2 III

Johannes Weiner wrote:

>> On Fri, May 09, 2008 at 05:17:13PM +0200, Johannes Weiner wrote:
>>> here is bootmem2, a memory block-oriented boot time allocator.
>>>
>>> Recent NUMA topologies broke the current bootmem's assumption that
>>> memory nodes provide non-overlapping and contiguous ranges of pages.
>> I'm still not sure that's a really good rationale for bootmem2.
>> e.g. the non continuous nodes are really special cases and there tends
>> to be enough memory at the beginning which is enough for boot time
>> use, so for those systems it would be quite reasonably to only 
>> put the continuous starts of the nodes into bootmem.
> 
> Hm, that would put the logic into arch-code.  I have no strong opinion
> about it.

In fact I suspect the current code will already work like that
implicitely. The aliasing is only a problem for the new "arbitary node
free_bootmem" right?

>> That said the bootmem code has gotten a little crufty and a clean
>> rewrite might be a good idea.
> 
> I agree completely.

The trouble is just that bootmem is used in early boot and early boot is
very subtle and getting it working over all architectures could be a
challenge. Not wanting to discourage you, but it's not exactly the
easiest part of the kernel to hack on.

-Andi
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