Le 03/06/2015 04:17, Chris Friesen a écrit :
On 06/02/2015 07:48 PM, Jay Pipes wrote:
On 06/02/2015 07:25 PM, Chris Friesen wrote:
In many cases only nova-compute can resolve races (resource tracking of
specific CPU cores, specific PCI devices, etc. in the face of parallel
scheduling) so unless we're going to guarantee no races then I think
claim requests should be a nova API call, and it should go all the way
down to nova-compute to make sure that the resources are actually
claimed.
That's actually how the system works today. And, IMHO, it's
inefficient. The
nova-compute node should be the final arbiter of whether a request
for resources
can be properly fulfilled by the hypervisor, however, the scheduler
should be
the thing that "owns" resource usage records for the partition of
resource
providers that the scheduler process is responsible for.
If the nova-compute node is still the final arbiter, what does it
actually mean to say that the scheduler "owns" the records?
That's not ambivalent. Considering that the placement decision is made
by the Scheduler(s) ( note the -s- ), it means that the scheduler is the
thing who owns the resource usage.
Of course, it also means that the compute node is only here as a
last-standing-man to make sure it can handle the request. But if it
can't, it has to report to the scheduler that the placement decision was
incorrect, so the scheduler can make adjustements if necessary.
-Sylvain
Chris
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