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Author SHA1 Message Date
Developer
265992c3db feat: per-actor mailbox backpressure with configurable overflow 
Add optional bounded mailboxes to prevent unbounded memory growth.
MailboxOverflow enum: DropNewest (discard incoming) or DropOldest
(evict oldest to make room). Default capacity=0 preserves unbounded
behavior for full backward compatibility.

messages_dropped counter added to WorkerStats for observability.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
 2026-02-12 11:54:16 +00:00
Developer
7d00e65a0a feat: load-aware actor placement + work stealing research 
Replace blind round-robin placement with load-aware strategy that reads
per-worker stats (actor count + mailbox depth) and biases toward lighter
workers. Falls back to round-robin when stats are equal (initial burst).

Deep research on work stealing across Tokio (steal-half, LIFO slot),
Go (M:N scheduler), BEAM (proactive migration), and ForkJoinPool.
Full actor migration is feasible but deferred due to message-loss window.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
 2026-02-12 11:46:53 +00:00
Developer
10cb0780b7 feat: stress tests, expanded benchmarks, and research extension 
Cycle 2 of the competitor analysis improvement loop.

Research additions:
- Kameo: async on tokio, dual bounded/unbounded mailbox (default 64),
  Erlang-style supervision links, vtable dispatch
- Actix: custom Vyukov lock-free MPSC queue (why it's fastest),
  256-message assertion guard (validates our budget), Context-as-Future

New stress tests (6):
- Message ordering preserved under small budget (budget=8)
- Multi-threaded: 50 senders × 100 msgs to one receiver (4 threads)
- Concurrent spawn+send of 200 actors (4 threads)
- 50-level chain spawning across 2 workers
- Panic isolation: 10 panicking + 10 healthy actors (4 threads)
- Sustained throughput: 10 batches of 100 msgs with interleaved ticks

New benchmark groups:
- msg_size: throughput and send_latency by message size (8B-4KB)
- contention: fanin (1-100 senders), cross_worker (1-4 threads)

All 57 tests pass (51 runtime_api + 5 transport + 1 doctest).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
 2026-02-12 11:24:33 +00:00
Developer
ef87f7e1b9 feat: per-actor message budget for tick fairness 
Research across ractor, tokio, Erlang/OTP BEAM, Linux CFS, and libuv
revealed that tick_all drained the entire mailbox per actor per tick,
allowing one hot actor to starve all others on the same worker.

- Add `actor_message_budget` to RuntimeConfig (default: 64 msgs/actor/tick)
- Modify tick_all to break after budget messages, yielding to next actor
- budget=0 restores unlimited (backward compatible) behavior
- 3 new fairness tests validating hot-cold actor scenarios
- New fairness benchmark group (cold_latency_under_pressure, throughput_by_budget)
- Fix RuntimeConfig struct literals across workspace crates

Inspired by BEAM's 4000-reduction budget and tokio's 128-op cooperative budget.
All 45 tests pass (42 original + 3 new).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
 2026-02-12 11:11:30 +00:00