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On Mon, 2019-06-17 at 16:45 +0800, Alex Xu wrote:
> 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.
we modified the spec intentionally to make upgradeing simple.
i don't be believe the concerns raised in the intial 2 emails are valid 
if we follow what was detailed in the spec.

we did take some steps to restrict what values you can set.
for example dedicated_cpu_set cannot be set if vcpu pin set is set.
technicall i belive we relaxed that to say we would ignore vcpu pin set in that case
be original i was pushing for it to be a hard error.

> 
> 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.
it should be enabled after all node are upgraded but not nessisarily before
all compute nodes are updated to use dedicated_cpu_set.


> 
> 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.
+1
> 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)
im not sure why we need to do this unless you are thinging this will be
done by a cli? e.g. like nova-manage.
> 4. reshape the inventories for existed instance for all the hosts.
should this not happen when the agent starts up?
> 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.
vcpu_pin_set is not the set of cpu used for pinning.
the operators should set dedicated_cpu_set and shared_cpu_set approprealy
at this point but in general they proably wont just copy it as host that
used vcpu_pin_set but were not used for pinned instances will be copied to
shared_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.
neither of these rule can be enforced. one of the requirements that dan smith had
for edge computeing is that we need to supprot upgraes with instance inplace.
> 
> 
> 
> Shewale, Bhagyashri <Bhagyashri.Shewale at 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:
> > 
> >    1. Flavor having extra specs (resources:PCPU=1), instance A
> >    2. 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 at redhat.com>
> > *Sent:* Thursday, June 13, 2019 8:32:02 PM
> > *To:* Shewale, Bhagyashri; openstack-discuss at lists.openstack.org;
> > openstack at fried.cc; sfinucan at redhat.com; jaypipes at 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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