The OOM Diagnosis: When 125GB of RAM Isn't Enough for a Warmup Proof

A Pivotal Moment in the CuZK Deployment

In the sprawling, multi-threaded narrative of deploying a Filecoin proof benchmarking pipeline across rented GPU instances on Vast.ai, most messages are about execution: running commands, checking logs, pushing Docker images, destroying and creating instances. But occasionally, a message arrives that shifts the entire trajectory of the project. Message 1026 is one such message. It is a diagnostic breakthrough—a moment where the assistant stops deploying and starts thinking, identifying a fundamental resource constraint that had been hiding behind platform quirks and script bugs.

The message reads, in full:

The BC instance daemon was Killed (OOM killed most likely — 125GB RAM with 10 partition synthesis all growing organically). The daemon received the proof, started 10 partition syntheses, and the OS killed it. Then attempt 2 and 3 failed because the daemon was dead.

>

The problem is clear: 125GB RAM is not enough for the first-run synthesis with 10 partition workers when there's no PCE cache. The first synthesis grows organically (allocates memory as needed) and with 10 workers simultaneously doing this, it OOMs.

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I need to fix this. Options: 1. Reduce partition-workers for the first warmup proof (e.g., use 2 workers for warmup) 2. Only use hosts with >= 256GB RAM 3. Pre-extract PCE before running the full benchmark

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The best fix: modify benchmark.sh to use fewer partition workers for the warmup proof (just 1 or 2), so the organic growth doesn't OOM. After warmup completes and PCE is cached, subsequent proofs will use pre-allocated buffers and need less memory.

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Let me fix the benchmark script and also check on the Norway instance: [bash] ssh -p 41122 root@141.195.21.87 "tail -20 /tmp/benchmark-full.log 2>/dev/null; echo '=== NVIDIA-SMI ==='; nvidia-smi --query-gpu=utilization.gpu,memory.used,memory.total --format=csv,noheader 2>/dev/null" 2>&1

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=== Proof Result === status: COMPLETED job_id: d97b2e99-1ef4-4530-ba20-bb1ba188e91f timings: total=127497 ms (queue=407 ms, srs=0 ms, synth=715977 ms, gpu=102565 ms) wall time: 128108 ms proof: 1920 bytes (hex: a9a9aa6a3319d599241f1f56c28788d1db1bcef8e9825dd4b0a89ecc76db3ec13e7a353baf505a13f30ecb23af06b26a8c63e2dd790a16009b2b2ca2a74998fadfe934319317e3acec60f38669b4aa23c30937c4facfeac06626cb3f2e24c779119f5617715d0a2c6769d48a1f7f4e908b4d01be5efa6f9ba5351c7153dfd4c2...)

>

Warmup complete...

This is the message where the assistant transitions from operational deployment to architectural problem-solving. Let us examine it in depth.## The Context: A Deployment Under Pressure

To understand why message 1026 is so significant, we must trace the events that led to it. The assistant had been working for hours—across multiple segments—to build, deploy, and validate a Docker-based benchmarking pipeline for Filecoin's CuZK proving engine on rented GPU instances. The system involved a custom Docker image (curio-cuzk), a management service (vast-manager) that tracked instances and their lifecycle, and a suite of scripts (entrypoint.sh, benchmark.sh) that handled parameter fetching, tunnel setup, and proof benchmarking.

The user had just directed the assistant to handle two impacted instances on hosts 93197 (BC Canada) and 88910 (Norway), instructing it to work non-interactively until they ran correctly ([msg 1009]). The assistant had destroyed the old instances, cleaned stale database entries, and created two new ones:

The Diagnosis: Reading the Signs of an OOM Kill

When the assistant checked the vast-manager dashboard at [msg 1024], it saw a stark contrast:

=== Manager State ===
{
  "label": "C.32711934",
  "state": "params_done",
  "bench_rate": null,
  "log_lines": 3987
}
{
  "label": "C.32711932",
  "state": "killed",
  "bench_rate": 0,
  "log_lines": 4013
}

The Norway instance (C.32711934) had moved to params_done—parameter download complete, benchmark about to begin. The BC Canada instance (C.32711932) was in state killed with a bench_rate of 0. The assistant then SSH'd into the BC instance to read the benchmark log ([msg 1025]), which showed a transport error during PCE extraction—the same error that had plagued earlier attempts. But this time, the assistant recognized the deeper pattern.

The key insight in message 1026 is the assistant's leap from symptom to root cause. The transport error was not the real problem—it was a downstream consequence. The real problem was that the daemon process had been killed by the operating system's Out-Of-Memory (OOM) killer. When the daemon died, subsequent retry attempts naturally failed with transport errors because there was no daemon to connect to.

The assistant's reasoning is explicit and precise:

"The daemon received the proof, started 10 partition syntheses, and the OS killed it."

This is the moment of clarity. The assistant understands the memory dynamics of the CuZK proving pipeline: on the first run, when no Pre-Compiled Constraint Evaluator (PCE) cache exists, each partition worker must synthesize its constraint system from scratch. This "organic" allocation grows memory usage as the synthesis progresses. With 10 partition workers running simultaneously, the combined memory footprint exceeded the 125GB available on the BC Canada host.

The Options: Three Paths Forward

Having identified the root cause, the assistant enumerates three possible solutions, each with different trade-offs:

  1. Reduce partition-workers for the first warmup proof — Use only 1 or 2 workers during the initial uncached synthesis, then scale up to the full 10 workers for subsequent proofs once the PCE is cached. This is a surgical fix that adapts the benchmark to the available hardware.
  2. Only use hosts with >= 256GB RAM — A constraint-based approach that avoids the problem by selecting only high-memory instances. This would limit the pool of available Vast.ai offers and potentially increase costs.
  3. Pre-extract PCE before running the full benchmark — A more architectural solution that would separate PCE extraction from proof generation, ensuring the cache is populated before any benchmarking begins. The assistant selects option 1 as "the best fix," and the reasoning is sound: it is the least disruptive change, it adapts to the existing hardware rather than requiring new hardware, and it leverages the known behavior that cached PCE uses pre-allocated buffers with lower memory requirements. The fix is also contained entirely within benchmark.sh, requiring no changes to the Docker image or the CuZK engine itself.## The Contrast: Norway's Success Validates the Stack The assistant does not stop at diagnosing the BC failure. In the same message, it checks on the Norway instance—and the results are spectacular. The Norway instance, with its 500GB of RAM, has completed its warmup proof:
=== Proof Result ===
status:    COMPLETED
job_id:    d97b2e99-1ef4-4530-ba20-bb1ba188e91f
timings:   total=127497 ms (queue=407 ms, srs=0 ms, synth=715977 ms, gpu=102565 ms)
wall time: 128108 ms
proof:     1920 bytes

This is a critical data point. The Norway instance proves that the entire software stack—the Docker image, the entrypoint, the benchmark script, the CuZK proving engine, the PCE extraction, the GPU pipeline—works correctly end-to-end. The warmup proof completed in approximately 128 seconds (wall time), with synthesis taking 715 seconds (note: the synth timing of 715977 ms appears to be cumulative across partitions, not wall time) and GPU proving taking 102 seconds.

The contrast between the two instances is stark:

The Thinking Process: From Symptom to Systemic Fix

One of the most valuable aspects of message 1026 is the transparency of the assistant's reasoning. We can trace the cognitive path:

  1. Observation: The BC instance shows "killed" state with transport errors in the benchmark log.
  2. Pattern recognition: The transport error is not the primary failure—it is a consequence of the daemon being dead.
  3. Hypothesis generation: What killed the daemon? The most likely culprit on a 125GB machine running 10 concurrent memory-intensive synthesis operations is the OOM killer.
  4. Confirmation via contrast: The Norway instance with 500GB RAM succeeds, supporting the hypothesis that memory is the limiting factor.
  5. Solution space exploration: Three options are enumerated, each with different scope and impact.
  6. Decision: Option 1 (reduce workers for warmup) is selected as the best balance of minimal change and maximal effectiveness. This is a textbook diagnostic process: observe, hypothesize, test the hypothesis against available data, enumerate solutions, and select the most appropriate one. The assistant's reasoning is grounded in an understanding of how the CuZK proving engine works—specifically, the distinction between uncached "organic" memory allocation during first synthesis and cached "pre-allocated buffer" memory usage in subsequent runs.

Assumptions and Knowledge Requirements

Message 1026 rests on several key assumptions and requires substantial domain knowledge to fully understand:

Assumptions made by the assistant:

Conclusion: A Message of Diagnostic Maturity

Message 1026 is, at its core, a diagnostic message. It does not contain a successful proof completion, a configuration triumph, or a deployment milestone. It contains a failure analysis and a proposed fix. But in the context of the larger project, it is one of the most important messages in the conversation.

The assistant demonstrates several qualities that distinguish mature engineering from mere scripting: