I'm thinking we should have recommended upgrade follow. If we give a lot of flexibility for the operator to have a lot combination of the value of vcpu_pin_set, dedicated_cpu_set and shared_cpu_set, then we have trouble in this email and have to do a lot of checks this email introduced also.

I'm thinking that the pre-request filter (which translates the cpu_policy=dedicated to PCPU request) should be enabled after all the node upgrades to the Train release. Before that, all the cpu_policy=dedicated instance still using the VCPU.

Trying to image the upgrade as below:

1. Rolling upgrade the compute node.

2. The upgraded compute node begins to report both VCPU and PCPU, but reshape for the existed inventories.

The upgraded node is still using the vcpu_pin_set config, or didn't set the vcpu_pin_config. Both in this two cases are reporting VCPU and PCPU same time. And the request with cpu_policy=dedicated still uses the VCPU. Then it is worked same as Stein release. And existed instance can be shelved/unshelved, migration and evacuate.

3. Disable the new request and operation for the instance to the hosts for dedicated instance. (it is kind of breaking our live-upgrade? I thought this will be a short interrupt for the control plane if that is available)

4. reshape the inventories for existed instance for all the hosts.

5. Enable the instance's new request and operation, also enable the pre-request filter.

6. Operator copies the value of vcpu_pin_set to dedicated_cpu_set. For the case of vcpu_pin_set isn't set, the value of dedicated_cpu_set should be all the cpu ids exclude shared_cpu_set if set.

Two rules at here:

1. The operator doesn't allow to change a different value for dedicated_cpu_set with vcpu_pin_set when any instance is running on the host.

2. The operator doesn't allow to change the value of dedicated_cpu_set and shared_cpu_set when any instance is running on the host.

Shewale, Bhagyashri <Bhagyashri.Shewale@nttdata.com> 于2019年6月14日周五下午4:42写道：

>> that is incorrect both a and by will be returned. the spec states that for host A we report an inventory of 4 VCPUs and

>> an inventory of 4 PCPUs and host B will have 1 inventory of 4 PCPUs so both host will be returned assuming

>> $<no. of cpus> <=4

Means if ``vcpu_pin_set`` is set in previous release then report both VCPU and PCPU as inventory (in Train) but this seems contradictory for example:

On Stein,

Configuration on compute node A:

vcpu_pin_set=0-3 (This will report 4 VCPUs inventory in placement database)

On Train:

vcpu_pin_set=0-3

The inventory will be reported as 4 VCPUs and 4 PCPUs in the placement db

Now say user wants to create instances as below:

Flavor having extra specs (resources:PCPU=1), instance A
Flavor having extra specs (resources:VCPU=1), instance B

For both instance requests, placement will return compute Node A.

Instance A: will be pinned to say 0 CPU

Instance B: will float on 0-3

To resolve above issue, I think it’s possible to detect whether the compute node was configured to be used for pinned instances if ``NumaTopology`` ``pinned_cpus`` attribute is not empty. In that case, vcpu_pin_set will be reported as PCPU otherwise VCPU.

Regards,

-Bhagyashri Shewale-

From: Sean Mooney <smooney@redhat.com>
Sent: Thursday, June 13, 2019 8:32:02 PM
To: Shewale, Bhagyashri; openstack-discuss@lists.openstack.org; openstack@fried.cc; sfinucan@redhat.com; jaypipes@gmail.com
Subject: Re: [nova] Spec: Standardize CPU resource tracking

On Wed, 2019-06-12 at 09:10 +0000, Shewale, Bhagyashri wrote:
> Hi All,
>
>
> Currently I am working on implementation of cpu pinning upgrade part as mentioned in the spec [1].
>
>
> While implementing the scheduler pre-filter as mentioned in [1], I have encountered one big issue:
>
>
> Proposed change in spec: In scheduler pre-filter we are going to alias request_spec.flavor.extra_spec and
> request_spec.image.properties form ``hw:cpu_policy`` to ``resources=(V|P)CPU:${flavor.vcpus}`` of existing instances.
>
>
> So when user will create a new instance or execute instance actions like shelve, unshelve, resize, evacuate and
> migration post upgrade it will go through scheduler pre-filter which will set alias for `hw:cpu_policy` in
> request_spec flavor ``extra specs`` and image metadata properties. In below particular case, it won’t work:-
>
>
> For example:
>
>
> I have two compute nodes say A and B:
>
>
> On Stein:
>
>
> Compute node A configurations:
>
> vcpu_pin_set=0-3 (used as dedicated CPU, This host is added in aggregate which has “pinned” metadata)
vcpu_pin_set does not mean that the host was used for pinned instances
https://that.guru/blog/cpu-resources/
>
>
> Compute node B Configuration:
>
> vcpu_pin_set=0-3 (used as dedicated CPU, This host is added in aggregate which has “pinned” metadata)
>
>
> On Train, two possible scenarios:
>
> Compute node A configurations: (Consider the new cpu pinning implementation is merged into Train)
>
> vcpu_pin_set=0-3 (Keep same settings as in Stein)
>
>
> Compute node B Configuration: (Consider the new cpu pinning implementation is merged into Train)
>
> cpu_dedicated_set=0-3 (change to the new config option)
>
>   1. Consider that one instance say `test ` is created using flavor having old extra specs (hw:cpu_policy=dedicated,
> "aggregate_instance_extra_specs:pinned": "true") in Stein release and now upgraded Nova to Train with the above
> configuration.
>   2. Now when user will perform instance action say shelve/unshelve scheduler pre-filter will change the
> request_spec flavor extra spec from ``hw:cpu_policy`` to ``resources=PCPU:$<no. of cpus>``
it wont remove hw:cpu_policy it will just change the resouces=VCPU:$<no. of cpus> ->   resources=PCPU:$<no. of cpus>

> which ultimately will return only compute node B from placement service.
that is incorrect both a and by will be returned. the spec states that for host A we report an inventory of 4 VCPUs and
an inventory of 4 PCPUs and host B will have 1 inventory of 4 PCPUs so both host will be returned assuming
$<no. of cpus> <=4

> Here, we expect it should have retuned both Compute A and Compute B.
it will
>   3. If user creates a new instance using old extra specs (hw:cpu_policy=dedicated,
> "aggregate_instance_extra_specs:pinned": "true") on Train release with the above configuration then it will return
> only compute node B from placement service where as it should have returned both compute Node A and B.
that is what would have happend in the stien version of the spec and we changed the spec specifically to ensure that
that wont happen. in the train version of the spec you will get both host as candates to prevent this upgrade impact.
>
> Problem: As Compute node A is still configured to be used to boot instances with dedicated CPUs same behavior as
> Stein, it will not be returned by placement service due to the changes in the scheduler pre-filter logic.
>
>
> Propose changes:
>
>
> Earlier in the spec [2]: The online data migration was proposed to change flavor extra specs and image metadata
> properties of request_spec and instance object. Based on the instance host, we can get the NumaTopology of the host
> which will contain the new configuration options set on the compute host. Based on the NumaTopology of host, we can
> change instance and request_spec flavor extra specs.
>
>   1. Remove cpu_policy from extra specs
>   2. Add “resources:PCPU=<count>” in extra specs
>
>
> We can also change the flavor extra specs and image metadata properties of instance and request_spec object using the
> reshape functionality.
>
>
> Please give us your feedback on the proposed solution so that we can update specs accordingly.
i am fairly stongly opposed to useing an online data migration to modify the request spec to reflect the host they
landed on. this speficic problem is why the spec was changed in the train cycle to report dual inventoryis of VCPU and
PCPU if vcpu_pin_set is the only option set or of no options are set.
>
>
> [1]: https://review.opendev.org/#/c/555081/28/specs/train/approved/cpu-resources.rst@451
>
> [2]: https://review.opendev.org/#/c/555081/23..28/specs/train/approved/cpu-resources.rst
>
>
> Thanks and Regards,
>
> -Bhagyashri Shewale-
>
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