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


  • To: "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
  • Date: Fri, 25 Jul 2008 07:53:33 +0100
  • Cc:
  • Delivery-date: Thu, 24 Jul 2008 23:53:54 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcjuIydCZb+ZOFoWEd2XagAWy6hiGQ==
  • Thread-topic: [Xen-devel] Memory allocation in NUMA system

On 25/7/08 04:34, "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx> wrote:

> Let's say we have a 2-node system, with node0 and node1's memory range
> being 0-0xc0000000 (<4G) and 0x100000000-0x1c0000000 (>4G) respectively.
> In that case, node1's memory is always preferred for domain memory
> allocation, no matter which node the created domain is pinned to. It
> results in performance penalty.
> 
> One possible fix is to specify all range for the domain memory
> allocation, which means local memory is preferred. This change may be
> restricted only to the domain pinned to one node for less impact.
> 
> One side effect is that the DMA memory size may be smaller, which makes
> device domain unhappy. This can be addressed by reserving node0 to be
> used lastly.

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?

 -- Keir



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