GPU Design · All levels
Verification, Performance & Bring-up: Tricky Q&A
Senior interview and review questions for Verification, Performance & Bring-up.
Section Q&A bank
Use these drills after completing all topics in Verification, Performance & Bring-up. Answer with workload context, mechanism proof, artifact, owner, and release decision.
Why do microbenchmarks pass while product workloads miss SLA?
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[INT][GPU][VERIFICATION-PERFORMANCE]
Q: Why do microbenchmarks pass while product workloads miss SLA?
A:
Isolated kernels hide runtime overheads, queue contention, and host-device synchronization that dominate end-to-end behavior.
FOLLOW-UP TRAP: Promoting changes based only on synthetic kernel benchmarks.How do you validate that counters remain trustworthy across releases?
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[INT][GPU][VERIFICATION-PERFORMANCE]
Q: How do you validate that counters remain trustworthy across releases?
A:
Use calibrated counter dictionaries, deterministic replay captures, and cross-checks against known golden traces after toolchain changes.
FOLLOW-UP TRAP: Assuming counter semantics are stable across firmware/driver updates.What is the minimum evidence for a post-silicon performance signoff?
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[INT][GPU][VERIFICATION-PERFORMANCE]
Q: What is the minimum evidence for a post-silicon performance signoff?
A:
Reproducible benchmark matrix, root-cause attribution for major gaps, and owner-signed closure for open regressions.
FOLLOW-UP TRAP: Using one successful bring-up run as release proof.When should stress-test failures block tapeout readiness claims?
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[INT][GPU][VERIFICATION-PERFORMANCE]
Q: When should stress-test failures block tapeout readiness claims?
A:
When thermal throttling or power excursions violate reliability margins on validated worst-case vectors.
FOLLOW-UP TRAP: Treating stress failures as lab-only anomalies.Q&A drill guide
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WORKLOAD -> BOTTLENECK -> METRIC -> CHANGE -> REGRESSIONSketch while answering
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PERF VERIFICATION LOOP
benchmark -> profile -> optimize -> verify correctness -> regressKey takeaways
Always pair micro-kernel metrics with end-to-end workload impact.
Lock toolchain, driver, and launch metadata before comparing performance results.
Common pitfalls
Optimizing occupancy without checking memory-system saturation.
Comparing profiler captures from different driver or compiler builds.
Declaring wins without reproducible accuracy and performance gates.