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[Xen-devel] How does the numa flag affect memory allocation?

  • To: <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Carb, Brian A" <Brian.Carb@xxxxxxxxxx>
  • Date: Tue, 20 Nov 2007 11:39:52 -0600
  • Delivery-date: Tue, 20 Nov 2007 09:41:36 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcgrnFsHOMMA+bCMS4ezfG6RanzHZA==
  • Thread-topic: How does the numa flag affect memory allocation?


I'm trying to get a full grasp of what the "numa" flag does in Xen.

It is my understanding that, with numa=on, Xen will try to allocate memory for a para VM from the same node as the CPUs that the VM's procs are pinned to. Thus, in a multi-node system, if we specify a pinning to a specific node's CPUs in a VM's config file, Xen will allocate the VM's initial memory from that same node at startup

My question is: does this location preference happen for all subsequent memory allocation? In other words, if I boot a VM configured with some initial memory and pinned to CPUs in node-X, change the pinning of the VM's procs to CPUs in node-Y, and then use "xm mem-set" to allocate more memory, does this new memory come from node-Y?

Also, does the numa flag influence things other than memory allocation?


brian carb
unisys corporation - malvern, pa


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