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

Paul Michali pc at michali.net
Fri Jun 10 13:05:37 UTC 2016


Thanks Daniel and Chris! I think that was the problem, I had configured
Nova flavor with a mem_page_size of 1024, and it should have been one of
the supported values.

I'll go through and check things out one more time, but I think that is the
problem. I still need to figure out what is going on with the neutron port
not being released - we have another person in my group who has seen the
same issue.

Regards,

PCM

On Fri, Jun 10, 2016 at 4:41 AM Daniel P. Berrange <berrange at redhat.com>
wrote:

> On Thu, Jun 09, 2016 at 12:35:06PM -0600, Chris Friesen wrote:
> > On 06/09/2016 05:15 AM, Paul Michali wrote:
> > > 1) On the host, I was seeing 32768 huge pages, of 2MB size.
> >
> > Please check the number of huge pages _per host numa node_.
> >
> > > 2) I changed mem_page_size from 1024 to 2048 in the flavor, and then
> when VMs
> > > were created, they were being evenly assigned to the two NUMA nodes.
> Each using
> > > 1024 huge pages. At this point I could create more than half, but when
> there
> > > were 1945 pages left, it failed to create a VM. Did it fail because the
> > > mem_page_size was 2048 and the available pages were 1945, even though
> we were
> > > only requesting 1024 pages?
> >
> > I do not think that "1024" is a valid page size (at least for x86).
>
> Correct, 4k, 2M and 1GB are valid page sizes.
>
> > Valid mem_page_size values are determined by the host CPU.  You do not
> need
> > a larger page size for flavors with larger memory sizes.
>
> Though note that page sizes should be a multiple of favour mem size
> unless you want to waste memory. eg if you have a flavour with 750MB
> RAM, then you probably don't want to use 1GB pages as it waste 250MB
>
> Regards,
> Daniel
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