v3.3.97 (UV_THREADPOOL_SIZE 64→8) was a decisive win — mean event-loop-delay at
70 active uploads dropped 200ms→~11ms (18×), rss 577→287MB, renderer healthy in
14/15 windows. But the user reports it is still not perfectly smooth. A focused
multi-agent investigation plus an adversarial review localized the residual to
TWO distinct, separately-measured spike sources:
1. Read-bursts. In the tail windows the file-read histogram inverts: FSReqCallback
climbs to 66-70 against threadpool=8 (~8.75× queue depth) while SimpleWriteWrap
(socket writes) collapses to 4-24 and mean delay rises to 30-42ms. GC is ruled
out (gcMax ≤27ms in every window). The clean inversion at a stable active=70 /
pending=1287 shows the reads are causal, not a symptom of a block elsewhere.
2. A suspected synchronous config-persist stall. save() → load() reparses the whole
electron-config.json — which now carries the 1287-job pending queue nested in
globalSettings plus full history — on every persist (because _atomicWrite nulls
the read cache), then _serializeForDisk JSON.stringify(…, null, 2) of all of it.
One tail sample (max 1021ms, heap spiking to 142MB) fits a large synchronous
structuredClone+stringify, but it is a single confounded point, so this build
only INSTRUMENTS the path rather than asserting the cause.
This release ships one behavioral change (kept to a single variable so the next
log attributes cleanly) plus measurement:
- highWaterMark 256KB→1MB in all five streaming read loops (lib/hosters.js,
doodstream/voe/vidmoly CHUNK_SIZE consts, and the inline value in
clouddrop-upload.js:108 — NOT the 16MB server chunk at clouddrop-upload.js:12).
UV_THREADPOOL_SIZE stays 8. This deepens each stream's read-ahead cushion from
~0.43s to ~1.7s at the per-stream rate, so a stream tolerates the threadpool
queue without starving its socket write, and cuts read-completion callbacks and
per-chunk Buffer allocations ~4×. Byte-correctness is unaffected: Content-Length
is preamble+fileSize+epilogue, independent of chunk size, and the chunk size
never touches the multipart boundaries. Fully reversible; a dedicated read-
concurrency semaphore is held in reserve if 1MB does not clear the bursts.
- config-store.js now times load() (the full reparse, which the account-failed
handler also hits per failure) and the _commit serialize, logging
`config-load …` / `config-serialize wall=…ms bytes=… hist=… queue=…` when the
synchronous work exceeds 20ms. load() is split into a timing wrapper + _loadImpl;
the timer is a no-op until main.js wires configStore.setPerfLog → logInfo.
The renderer batch-drain fix for the one observed 243ms longtask is intentionally
deferred: that jank is downstream of the main-thread read-burst flooding IPC, so
fix#1 should make it self-heal; bundling it would confound the measurement and
touch the progress hot path. All 397 tests pass.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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