This reverts the image-pool migration (commit 5629ba6). The bench
(bench_pool_concurrency / POOL-CONCURRENCY.md) measured the one pool it could
isolate — the thumbnail decode semaphore — and found flat throughput, p99 AND
peak RSS (137 MiB) from K=1..16: shrink-on-load already makes each decode
RAM-cheap, so sizing it to the CFS quota gains nothing measurable. Adding code
without a measured benefit isn't worth it.
Kept: the effective_parallelism() helper (it has a *measured* win in the Tokio
runtime — benches/RUNTIME.md) and the benchmark itself (reusable). The ffmpeg
video fan-out has a plausible a-priori case (one OS process per permit) but is
left as a future, deliberately-measured change rather than shipped on
speculation. Doc updated to record the decision.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JG5yYZ9s868mJwqT2Qz7ez
Adds Part B (peak RSS for K concurrent decodes) to bench_pool_concurrency and
records the findings in benches/POOL-CONCURRENCY.md.
Honest result: under a 2-core quota the thumbnail decode pool shows flat
throughput, p99, AND peak RSS (137 MiB) from K=1..16 — shrink-on-load already
made each decode RAM-cheap, so over-permitting costs nothing measurable here.
The effective_parallelism() migration is therefore a correctness/consistency
change with no downside, mainly protecting the transcode + ffmpeg pools (and
extreme host-core/quota ratios) this box can't reproduce — not a throughput win.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JG5yYZ9s868mJwqT2Qz7ez
Claude