Gary
Firstly, thanks for your review very much.
The pci_stats is calculated in the resource tracker in the compute
node and is also saved in compute_node, I think currently the scheduler depends
on the information provided by the compute_node table so this method should fit
into current framework.
Please notice that the scheduler only decide the host that can meet
the requirement, and it's the resource tracker in compute node that will do the
real device allocation. So if scheduler does not get the latest information, it
may either can't find the host, or, it finds a host with wrong information and
the re-try mechanism should work. Anyway, this is same to other compute nodes
information like free_ram or free_vcpus, right?
But you does remind me one thing, that if a hot plug happens , after
the resource tracker select the device and before the instance is really
created. Possibly the virt driver need check the requirement before create the
domain. But this race condition chain will not end. After all, there are window
between the virt driver check and the instance creation, and no idea how can we
guarantee this.
Thanks
--jyh
From: Gary Kotton [mailto:gkot...@vmware.com]
Sent: Wednesday, August 28, 2013 2:19 AM
To: OpenStack Development Mailing List (openstack-dev@lists.openstack.org)
Subject: [openstack-dev] [Nova] Scheduler support for PCI passthrough
Hi,
Whilst reviewing the code I think that I have stumbled on an issue (I hope that
I am mistaken). The change set (https://review.openstack.org/#/c/35749/)
expects pci stats to be returned from the host. There are a number of issues
here that I have concern with an would like to know what the process is for
addressing the fact that the compute node may not provide these statistics, for
example, this could be due to the fact that the driver has not been updated to
return the pci stats or this could be if the scheduler has been upgraded prior
to the compute node (what is the process for the upgrade).
Thanks
Gary
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