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Re: [Xen-devel] Memory allocation in NUMA system

To: Andre Przywara <andre.przywara@xxxxxxx>
Subject: Re: [Xen-devel] Memory allocation in NUMA system
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Mon, 28 Jul 2008 13:38:39 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx>
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On 28/7/08 13:21, "Andre Przywara" <andre.przywara@xxxxxxx> wrote:

> Mmh, why not check this in in 3.3? I have noticed this problem already a
> year ago and was having some other kind of fix for it (which actually
> prefered nodes over zones):
> http://lists.xensource.com/archives/html/xen-devel/2007-12/msg00831.html
> I think this is a somewhat serious issue on NUMA machines, since with
> the automatic pinning now active (new in 3.3!) many domains will end up
> with remote memory _all the time_. So I think of this as a bugfix.
> Actually I have dma_bitsize=30 hardwired in my Grub's menu.lst for some
> months now...

Well, fine, but unfortunately the patch breaks ia64 and doesn't even work
properly:
 - why should NUMA node 0 be the one that overlaps with default DMA memory?
 - a 'large' NUMA node 0 will cause dma_bitsize to be set much larger than
it is currently, thus breaking its original intent.

 -- Keir



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