NCA Performance Optimization & Debugging 2

Question 1

Which NVIDIA tool provides real-time GPU utilization, memory usage, and temperature monitoring from the command line?

Accepted Answer

nvidia-smi

Answer

nvidia-smi (NVIDIA System Management Interface) provides real-time monitoring of GPU metrics including utilization, memory, and temperature directly from the terminal.

Question 2

A CUDA kernel achieves only 40% of theoretical memory bandwidth. What is the most likely cause?

Accepted Answer

Uncoalesced global memory accesses

Answer

Uncoalesced global memory accesses force the GPU to issue multiple memory transactions instead of one, significantly reducing effective bandwidth utilization.

Question 3

In Nsight Compute, a kernel shows high 'Stall: Long Scoreboard' metric. What does this indicate?

Accepted Answer

Threads are stalled waiting for global memory loads to complete

Answer

Long Scoreboard stalls indicate threads are waiting for data from global memory loads, pointing to a memory-bound kernel needing better latency hiding or access pattern optimization.

Question 4

Which technique most effectively hides global memory latency in CUDA kernels?

Accepted Answer

Increasing the number of active warps per SM

Answer

Higher occupancy (more active warps per SM) allows the GPU scheduler to switch to ready warps while others wait for memory, hiding latency effectively.

Question 5

What does the CUDA event timing API measure that CPU timers cannot accurately capture?

Accepted Answer

Precise GPU kernel execution time excluding CPU overhead

Answer

CUDA events are recorded on the GPU timeline and measure actual kernel execution time without CPU-side scheduling jitter or synchronization overhead.

(NCA) NVIDIA-Certified Associate Practice Test

(NCA) NVIDIA-Certified Associate Practice Test

NCA Performance Optimization & Debugging 2