VMWare Video Memory Filter

VMWare Video Memory Filter - A filter scheduler for performing calculations using video memory

Problem Description
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The nova VMWare driver in Juno does not allow an instance to have a specific video memory, which means the default video memory (4 MB) is set by VMWare vCenter.

A Blueprint to support video memory for instances spawned using VMWare driver is submitted for Kilo
https://blueprints.launchpad.net/nova/+spec/vmware-driver-support-for-video-memory

This BP is an extension of the above mentioned BP

VMWare vCenter allows setting of Video Memory of the VM. The video memory allocation is evenly divided - Half the video memory is reserved on the hardware GPU, while the other half is reserved via host RAM. A maximum of 512 MB video can be assigned to a VM, which means a max of 256 MB is on hardware GPU for a VM. If a VM has video memory assigned and all the hardware GPU is already reserved for other VMs, then software 3D rendering will be used, which means all of the instance’s video memory will be on host RAM. By default the vCenter sets the graphics rendering to “Automatic”, which means if hardware GPU is not available, video memory is set on host RAM and software 3D rendering will be used.

The vCenter does not provide any API which returns the free video memory on the hardware GPU. Hence when a instance requires video memory, the scheduler calculation for a valid host can happen on the free host memory since vCenter by default uses host memory if video memory on hardware GPU is not available.

Proposed Change
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A new scheduler filter “VMWareVideoMemoryFilter” which extends RamFilter.
The VMWareVideoMemoryFilter will return a host as a valid host if the usable_ram > (requested_ram + video_ram)

The def host_passes() would be overridden in this class

The def _get_ram_allocation_ratio() will NOT be overridden as the allocation ratio will be the same as defined for RamFilter