Hello Nova team,
During the Cyborg discussion at Rocky PTG, we proposed a flow for FPGAs
wherein the request spec asks for a device type as a resource class, and
optionally a function (such as encryption) in the extra specs. This does not
seem to work well for the usage model that I'll describe below.
An FPGA device may implement more than one function. For example, it may
implement both compression and encryption. Say a cluster has 10 devices of
device type X, and each of them is programmed to offer 2 instances of function
A and 4 instances of function B. More specifically, the device may implement 6
PCI functions, with 2 of them tied to function A, and the other 4 tied to
function B. So, we could have 6 separate instances accessing functions on the
same device.
In the current flow, the device type X is modeled as a resource class, so
Placement will count how many of them are in use. A flavor for 'RC
device-type-X + function A' will consume one instance of the RC device-type-X.
But this is not right because this precludes other functions on the same device
instance from getting used.
One way to solve this is to declare functions A and B as resource classes
themselves and have the flavor request the function RC. Placement will then
correctly count the function instances. However, there is still a problem: if
the requested function A is not available, Placement will return an empty list
of RPs, but we need some way to reprogram some device to create an instance of
function A.
Regards,
Sundar
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