The 12 MB Question: A Moment of Verification in the cuzk Memory Manager Deployment

ssh -p 40612 root@141.0.85.211 'ps -o pid,rss,vsz,comm -p 28410'
    PID   RSS    VSZ COMMAND
  28410 12384 4179204 cuzk

At first glance, this message ([msg 2322]) appears trivial: a single SSH command querying the process table for a running daemon, returning three columns of numbers. But in the arc of the opencode session, this brief exchange represents a pivotal moment of verification — a sanity check performed just before unleashing a stress test on a newly deployed, budget-based memory manager for the cuzk GPU proving engine. The 12,384 KB resident memory and the 4,179,204 KB virtual address space tell a story about what has already happened, what is about to happen, and the careful reasoning required to deploy a memory-constrained system into production.

The Context: A Memory Manager Goes to Production

To understand why this message exists, one must trace the session's trajectory. Over the preceding messages, the assistant had designed, implemented, and validated a comprehensive unified memory manager for cuzk — the GPU-based proof generation engine at the heart of a Filecoin storage proving pipeline. The old architecture used a static partition_workers semaphore that naively limited concurrency without accounting for actual memory consumption. The new system introduced a MemoryBudget that tracks all major consumers — SRS pinned memory (~44 GiB for PoRep-32G), PCE heap allocations (~26 GiB), and synthesis working sets (~14 GiB per partition) — under a single byte-level budget, auto-detected from system RAM or explicitly configured.

The implementation had been committed, tested with real 32 GiB PoRep data across all 10 circuits (130M constraints each), and the changes were ready for deployment. The remote target was a machine with 755 GiB RAM, an RTX 5090 (32 GiB VRAM), and 64 cores — a production-class proving node already running Curio but not currently active with cuzk ([msg 2298]). The existing configuration at /tmp/cuzk-run-config.toml still used the deprecated preload and partition_workers fields ([msg 2301]), confirming the need for an upgrade.

The Deployment Pipeline

The assistant built a new binary using a minimal CUDA 13.0.2 devel Docker image (Dockerfile.cuzk-rebuild), extracted it from a scratch-based container using docker cp ([msg 2309]), uploaded it to the remote machine via SCP ([msg 2310]), and hot-swapped the daemon by copying it over the existing binary at /usr/local/bin/cuzk ([msg 2318]). A backup was created as cuzk.bak — a prudent measure when replacing a production binary.

A test configuration was then crafted to exercise the memory budget under tight constraints ([msg 2315]):

[memory]
total_budget = "100GiB"
safety_margin = "0GiB"
eviction_min_idle = "5m"

The rationale was deliberate: on a 755 GiB machine, a 100 GiB budget would force the memory manager to throttle concurrency. With SRS (~44 GiB) and PCE (~26 GiB) consuming 70 GiB baseline, only ~30 GiB would remain for working sets — approximately two partitions at 14 GiB each. This was a stress test designed to validate that the budget system actually gates admission, rather than allowing unbounded memory growth.

The Startup and the Wrong PID

The daemon started successfully with PID 28410 ([msg 2319]). The startup logs confirmed the memory budget was initialized correctly: total_budget_gib=100, max_partitions_in_budget=7, and the synthesis dispatcher started in "budget-gated" mode. No SRS preload occurred — on-demand loading was working.

But then came a small debugging hiccup. In [msg 2320], the assistant attempted to check the daemon's RSS before sending proofs:

ps -o pid,rss,vsz,comm -p $(pgrep -f cuzk-daemon)

This returned PID 28502 with RSS 3452 KB — but the command name was bash, not cuzk. The pgrep -f cuzk-daemon had matched the SSH command itself (which contained "cuzk-daemon" in its argument string), not the actual daemon. This is a classic pgrep -f pitfall: the pattern matches anywhere in the full command line, including SSH arguments.

The assistant caught this in [msg 2321], running a more specific pgrep -f "cuzk.*memtest" which correctly returned PID 28410. This set the stage for the subject message.## The Message Itself: What the Numbers Reveal

The subject message is straightforward:

ssh -p 40612 root@141.0.85.211 'ps -o pid,rss,vsz,comm -p 28410'
    PID   RSS    VSZ COMMAND
  28410 12384 4179204 cuzk

PID 28410 is confirmed as the cuzk daemon. Its resident set size (RSS) is 12,384 KB — approximately 12 MB. Its virtual memory size (VSZ) is 4,179,204 KB — approximately 4 GB. The stark disparity between RSS and VSZ is characteristic of a process that has mapped a large address space (likely memory-mapped files or GPU allocations) but has not yet faulted those pages into physical RAM. At this point, the daemon has just started, loaded its configuration, and initialized the memory budget — but no proofs have been processed, so no SRS data has been loaded and no PCE has been extracted.

The 12 MB RSS is a reassuring baseline. It tells the assistant that the daemon is alive, responsive, and not leaking memory at startup. The 4 GB VSZ hints at the memory-mapped parameter cache or pre-allocated GPU buffers. But the real test — whether the budget system correctly gates concurrency under load — is yet to come.

Assumptions and Their Risks

This message, like all debugging checkpoints, rests on several assumptions. The assistant assumes that PID 28410 is the correct process and that the ps output reflects a healthy daemon state. It assumes that the memory budget initialization logged in the startup messages is accurate and that the budget will be enforced during proof processing. It assumes that the on-demand SRS loading (rather than preload) will work correctly under concurrent pressure — a critical behavioral change from the old configuration which explicitly preloaded ["porep-32g"].

There is also an implicit assumption about the test environment: that the 100 GiB budget is sufficient to prevent OOM while still being tight enough to demonstrate throttling. On a machine with 755 GiB total RAM and 528 GiB available ([msg 2298]), a 100 GiB cap is deliberately restrictive. But the assistant has not yet accounted for the memory consumed by other processes — Curio itself is running with 226,548 KB RSS ([msg 2299]), and the system has 227 GiB used before cuzk even starts. The safety_margin = "0GiB" configuration is aggressive; it assumes the budget calculation is perfectly accurate and that no unexpected memory consumption will occur from co-located services.

The Thinking Process Visible in the Reasoning

The assistant's reasoning, visible in the surrounding messages, reveals a methodical deployment strategy. In [msg 2303], the assistant enumerated the remote machine's resources and noted the config gaps. In [msg 2315], it explicitly calculated the expected memory partitioning: "SRS ~44 GiB + PCE ~26 GiB = 70 GiB baseline... ~30 GiB for working set = ~2 partitions at 14 GiB each." This arithmetic informed the choice of a 100 GiB budget — tight enough to force contention, loose enough to allow meaningful work.

The debugging of the wrong PID in [msg 2320]-[msg 2321] demonstrates a healthy skepticism of tool output. The assistant did not blindly trust the first pgrep result; it noticed the command name was bash and refined the query. This attention to detail — verifying that the correct process is being monitored — is the difference between a valid experiment and a misleading one.

Output Knowledge Created

This message creates concrete, actionable knowledge: the cuzk daemon is running, it has the expected PID, its memory footprint at idle is minimal (12 MB RSS), and it is ready to receive proof requests. This baseline measurement is essential because subsequent measurements of RSS growth during proof processing will be compared against this starting point. Without this checkpoint, a later spike to 300 GB RSS could not be properly attributed to proof processing versus a startup leak.

The message also implicitly confirms that the hot-swap succeeded — the binary at /usr/local/bin/cuzk was replaced and the new version started without crashes, linking errors, or configuration parsing failures. This is a non-trivial validation for a GPU-accelerated binary built in a CUDA 13.0.2 Docker environment and deployed to a host with different driver versions.

What Happened Next

The story does not end with this clean baseline. In the subsequent chunk (Chunk 1 of Segment 17), the assistant would send proofs and immediately encounter a runtime panic: "Cannot block the current thread from within a runtime" at engine.rs:913. The evictor callback, called from the async acquire() loop, used blocking_lock() on a tokio Mutex — a classic async-blocking bug. The fix (replacing blocking_lock() with try_lock()) would be deployed, but further testing would reveal concurrency bottlenecks and ultimately an OOM kill when the budget was set too generously.

But at this moment — message [msg 2322] — none of that has happened yet. The daemon sits at 12 MB RSS, waiting. The assistant has done everything right: built the binary, deployed it, configured it, verified it. The 12,384 KB is a breath held before the plunge.

Conclusion

The subject message is a mundane technical artifact — a process table query — that gains significance from its context. It represents the culmination of a complex deployment pipeline (Docker build, binary extraction, SCP upload, hot-swap, config write, process verification) and the beginning of a stress test that would expose real-world bugs in the new memory manager. It demonstrates the importance of baseline measurements, the pitfalls of process matching with pgrep -f, and the methodical reasoning required to deploy critical infrastructure software. In the narrative of the opencode session, this message is the calm before the storm — a single data point that makes the subsequent crash meaningful.