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Occupancy and Register Pressure
Occupancy is the fraction of an SM's 64 warp slots that are resident, and it is capped by the 65,536 registers and 228 KB of shared memory each block consumes. It decides how much memory latency the hardware can hide for free, but the fastest kernels on a GPU routinely run at 25 percent, so the interview skill is knowing when to raise it and when to stop.
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CUDA, Triton & Kernel EngineeringExplain occupancy and register pressure: launch bounds, spills, the calculator, and why 50% occupancy can beat 100%.→CUDA, Triton & Kernel EngineeringYou added three local variables to a working kernel and it got 30 percent slower. Explain what happened and how you would confirm it.→GPU & Accelerator ArchitectureA kernel runs at 25% occupancy. Is that a problem? Walk me through what occupancy buys and when you would leave it low on purpose.→GPU & Accelerator ArchitectureWalk me through the CUDA execution model: what are grids, blocks and warps, and what does the hardware actually schedule?→CUDA, Triton & Kernel EngineeringHere is an Nsight Compute report for a slow kernel. Read it, name the bottleneck, and tell me what you would change.→GPU & Accelerator ArchitectureDescribe the GPU memory hierarchy. Where can a byte live on an H100, and what does each level cost?→