I’m trying to figure out whether GPU-direct-video would be suitable for video as feedback sensor in control loops. Signal latency is the killer requirement. I’m lacking some benchmarks as justification for investment in a project involving high speed CoaXPress camera’s, grabbers etc.
As a reference I have a 256x256x8bit image coming in at 5KHz frame rate via CoaXpress (Kaya/Euresys/Matrox/undecided as yet).
- Frame grabber sends data to CPU system memory. (22usec @ 3GB/sec CXP6 x 4)
- Frame grabber notifies the CPU of completed frame transferred using an interrupt. The time for this is reported to me as 12us on a typical i7, and includes all the system delays (FIFO , PCIe , DDR , interrupt)
- The CPU instructs the GPU to fetch the frame from system memory. Time for this depends on the GPU model.
- Transport to GPU memory (4usec @ 15GB/sec PCIe3.0x16)
- Is there a need to reprogram this cycle per frame?
Thus the total latency will be 22us + 12us + GPU latency + 4usec + reprogramming?
Anybody having having experience and these numbers?