Segment 21

In this sub-session, the assistant shifted focus from synthesis ordering to a performance investigation of GPU utilization. Despite a large backlog of synthesized partitions waiting for GPU proving, GPU compute utilization hovered around 50% with multi-second idle gaps. The assistant traced the GPU worker hot path and identified two potential bottlenecks: tracker lock contention with malloc_trim calls in the finalizer, and possible serialization via a C++ mutex in the two-phase prove flow. Rather than guessing, the assistant added precise timing instrumentation to the GPU worker loop (tracking each step between prove_start calls), the spawn_blocking GPU prove call (separating mutex wait from compute), and the finalizer (timing prove_finish, reservation drop, tracker lock wait, process_partition_result, and malloc_trim). The instrumentation uses Instant::now() with GPU_TIMING/FIN_TIMING log prefixes for easy grep analysis. The next step is to deploy the instrumented binary, gather logs from a live workload, and pinpoint the actual cause of the multi-second gaps.

The Evidence Imperative: From Priority Queues to Precision Instrumentation in the cuzk GPU Utilization Investigation 3546 words

Chunks

• The Long Tail of Scheduling: From Budget Management to Priority Queues in the cuzk Proving Pipeline
  2227 words
• The Evidence Imperative: How Instrumentation Replaced Guessing in the cuzk GPU Utilization Investigation
  2137 words