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[nova][scheduler] - Stack VMs based on RAM


On 4/19/2019 4:38 PM, melanie witt wrote:
> I agree it sounds like your overcommit settings are not being honored. 
> Placement will filter hosts taking overcommit into account, and if it 
> doesn't have the values you set, then it will return more hosts than the 
> RamFilter would filter, causing the difference in behavior.
> 
> To debug this further, you need to start looking at what values 
> placement has for the allocation ratios. You can do this by installing 
> the osc-placement plugin [1] for the openstackclient. Once installed, 
> you can do 'openstack resource provider inventory list <compute host 
> UUID>' to see what allocation ratios are being used on a given compute 
> host. If they're not 1.0, that would explain why it's returning too many 
> hosts. If that's the case, next step would be trying to figure out why 
> the values you're setting in nova.conf on the compute host (I assume you 
> made sure to restart nova-compute after setting) are not being 
> transferred to placement like they should be.

Some more background on how placement is involved here:

https://docs.openstack.org/nova/latest/admin/configuration/schedulers.html#allocation-ratios

https://specs.openstack.org/openstack/nova-specs/specs/stein/implemented/initial-allocation-ratios.html

-- 

Thanks,

Matt