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


  • To: "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx>
  • From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
  • Date: Fri, 25 Jul 2008 08:27:07 +0100
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Fri, 25 Jul 2008 00:27:28 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcjuJ9eyFiuw51obEd2XagAWy6hiGQ==
  • Thread-topic: [Xen-devel] Memory allocation in NUMA system

On 25/7/08 08:22, "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx> wrote:

>> Doesn't your solution amount to what we already do, for the 2-node example?
>> i.e., node0 would not be chosen until node1 is exhausted?
>> 
> Oh, what I mean is:
> With the above possible fix, the domain memory is allocated from the
> node it pinned to. As node0's memory is precious for DMA, it's suggested
> to pin VMs to other nodes firstly.
> 
> And for non-pinned VM, we can stick to the original method.

How about by default we guarantee no more than 25% of a node's memory is
classed as 'DMA memory', and we reduce the DMA address width variable in Xen
to ensure that?

So, in your example, we would reduce dma_bitsize to 30.

 -- Keir



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