Advanced

Occupancy and Register Pressure

Occupancy measures how many warps are resident relative to an SM’s limit. Registers, shared memory and launch shape constrain it, but higher occupancy is not always faster.

This concept is part of Premium, which includes all concepts, course lessons and answers.

Get Premium · ₹2,000 / $256 months of access · one payment · no auto-renew

RELATED CONCEPTS

GPU Execution Model CUDA Programming Model Shared Memory and Bank Conflicts Tiled Matrix Multiplication Profiling with Nsight FlashAttention Internals

LESSONS THAT TEACH THIS

Kernels and the MachineA warp is the unit of execution, and every kernel bug starts there14 min→Kernels and the MachineOccupancy is a means, and treating it as the goal makes kernels slower16 min→Kernels and the MachineShared memory is a manual cache with a bank conflict waiting in it17 min→

PRACTICE THIS IN REAL QUESTIONS

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.→CUDA, Triton & Kernel EngineeringA CUDA upgrade improves warm runs but slows the first request. Would you ship it?→