NCP-GENL GPU Acceleration and Optimization Practice Question
When profiling an application with NVIDIA Nsight Systems, you notice a long gap between kernel execution blocks on the GPU timeline. What is the most likely cause?
⚠ Common exam trap
Candidates often attribute these gaps to kernel execution time or network latency, ignoring the role of the host CPU and synchronization primitives in managing the GPU task queue execution flow.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Excessive host-side synchronization calls.
Long gaps in the GPU timeline usually indicate host-side synchronization, such as explicit cudaDeviceSynchronize() calls or CPU-bound code that is stalling the kernel launch queue. In production systems, unnecessary CPU-to-GPU synchronization forces the GPU to remain idle while waiting for the CPU to catch up, directly impacting system-wide latency and violating the principle of asynchronous task pipelining necessary for optimal GPU utilization.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The GPU is overheating and triggering thermal throttling.
Why it's wrong here
Thermal throttling generally results in lower clock speeds, which show up as longer execution times for kernels rather than empty gaps in the timeline. The GPU would still be processing, just at a slower rate. Gaps in the timeline imply the hardware is completely idle, not just running slowly.
- ✓
Excessive host-side synchronization calls.
Why this is correct
Explicit synchronization points force the CPU to wait for the GPU to finish all previous tasks before continuing. These gaps represent the time the GPU spends waiting for the CPU to process logic and issue new work, effectively serializing the pipeline and creating idle time on the GPU execution timeline.
- ✗
The PCIe bus is saturated with high-frequency data.
Why it's wrong here
PCIe saturation would result in long data transfer blocks (HtoD or DtoH) on the timeline, not empty gaps. If the bus were saturated, the GPU would likely be busy processing the data being transferred, or the timeline would show heavy transfer activity, not a lack of any activity at all.
- ✗
The kernel is launching with an invalid thread block size.
Why it's wrong here
Invalid block sizes typically result in kernel launch errors or execution failures, not timeline gaps. If the configuration were invalid, the driver would return an error code immediately. Timeline gaps indicate that the application is running correctly but is failing to keep the GPU pipeline fed with new work.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official NVIDIA exam blueprint
This NCP-GENL practice question is part of Courseiva's free NVIDIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the NCP-GENL exam.