[nova] Mempage fun
chris.friesen at windriver.com
Thu Jan 10 16:08:05 UTC 2019
On 1/8/2019 12:38 PM, Stephen Finucane wrote:
> I have (1) fixed here:
> That said, I'm not sure if it's the best thing to do. From what I'm
> hearing, it seems the advice we should be giving is to not mix
> instances with/without NUMA topologies, with/without hugepages and
> with/without CPU pinning. We've only documented the latter, as
> discussed on this related bug by cfriesen:
> Given that we should be advising folks not to mix these (something I
> wasn't aware of until now), what does the original patch actually give
I think we should look at it from the other direction...what is the
ultimate *desired* behaviour?
Personally, I'm coming at it from a "small-cloud" perspective where we
may only have one or two compute nodes. As such, the host-aggregate
solution doesn't really work.
I would like to be able to run cpu-pinned and cpu-shared instances on
the same node. I would like to run small-page (with overcommit) and
huge-page (without overcommit) instances on the same node. I would like
to run cpu-shared/small-page instances (which float over the whole host)
on the same host as a cpu-pinned/small-page instance (which is pinned to
specific NUMA nodes).
We have a warning in the docs currently that is specifically for
separating CPU-pinned and CPU-shared instances, but we also have a spec
that plans to specifically support that case. The way the code is
currently written we also need to separate NUMA-affined small-page
instances from non-NUMA-affined small-page instances, but I think that's
a bug, not a sensible design.
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