[openstack-dev] [nova] overhead_pin_set option

Sahid Orentino Ferdjaoui sferdjao at redhat.com
Wed Oct 11 09:14:43 UTC 2017

Some workloads require to have hypervisor overheads to be isolated
from the set of pCPUs running guest vCPUs threads.

For libvirt driver we have introduced the emulator threads placements
which provides an option to reserve an additional host CPU per guest
to pin the emulator threads on [0].

To extend the flexibility and address use-cases where resources on
hosts are limited. We are introducing 'overhead_pin_set' option on
compute node. Operators will have ability to reserve host CPUs for
hypervisor overhead.

For case of libvirt driver we are extending the flavor property
hw:emulator_threads_policy to accept 'host' value, meaning that the
guests configured to use hw:emulator_threads_policy=host will have
their emulator threads running on the set of pCPUs configured with
'overhead_pin_set' option.

The blueprint [1] on launchpad.net, patches [2] and spec updated [3]

[0] https://specs.openstack.org/openstack/nova-specs/specs/pike/implemented/libvirt-emulator-threads-policy.html
[1] https://blueprints.launchpad.net/nova/+spec/overhead-pin-set
[2] https://review.openstack.org/#/c/510897/
[3] https://review.openstack.org/#/c/511188/

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