[openstack-dev] [nova] NUMA, huge pages, and scheduling

Paul Michali pc at michali.net
Tue Jun 14 17:09:43 UTC 2016

Great info Chris and thanks for confirming the assignment of blocks of
pages to a numa node.

I'm still struggling with why each VM is being assigned to NUMA node 0. Any
ideas on where I should look to see why Nova is not using NUMA id 1?



On Tue, Jun 14, 2016 at 10:29 AM Chris Friesen <chris.friesen at windriver.com>

> On 06/13/2016 02:17 PM, Paul Michali wrote:
> > Hmm... I tried Friday and again today, and I'm not seeing the VMs being
> evenly
> > created on the NUMA nodes. Every Cirros VM is created on nodeid 0.
> >
> > I have the m1/small flavor (@GB) selected and am using hw:numa_nodes=1
> and
> > hw:mem_page_size=2048 flavor-key settings. Each VM is consuming 1024
> huge pages
> > (of size 2MB), but is on nodeid 0 always. Also, it seems that when I
> reach 1/2
> > of the total number of huge pages used, libvirt gives an error saying
> there is
> > not enough memory to create the VM. Is it expected that the huge pages
> are
> > "allocated" to each NUMA node?
> Yes, any given memory page exists on one NUMA node, and a single-NUMA-node
> VM
> will be constrained to a single host NUMA node and will use memory from
> that
> host NUMA node.
> You can see and/or adjust how many hugepages are available on each NUMA
> node via
> /sys/devices/system/node/nodeX/hugepages/hugepages-2048kB/* where X is the
> host
> NUMA node number.
> Chris
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