[openstack-dev] [nova] NUMA-aware live migration: easy but incomplete vs complete but hard

Artom Lifshitz alifshit at redhat.com
Thu Jun 21 13:04:23 UTC 2018


>
> As I understand it, Artom is proposing to have a larger race window,
> essentially
> from when the scheduler selects a node until the resource audit runs on
> that node.
>

Exactly. When writing the spec I thought we could just call the resource
tracker to claim the resources when the migration was done. However, when I
started looking at the code in reaction to Sahid's feedback, I noticed that
there's no way to do it without the MoveClaim context (right?)

Keep in mind, we're not making any race windows worse - I'm proposing
keeping the status quo and fixing it later with NUMA in placement (or the
resource tracker if we can swing it).

The resource tracker stuff is just so... opaque. For instance, the original
patch [1] uses a mutated_migration_context around the pre_live_migration
call to the libvirt driver. Would I still need to do that? Why or why not?

At this point we need to commit to something and roll with it, so I'm
sticking to the "easy way". If it gets shut down in code review, at least
we'll have certainty on how to approach this next cycle.

[1] https://review.openstack.org/#/c/244489/

>
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