transport and messaging perf review

[Basedfloppa]

1 - Bytes for payloads: make operation clones O(1)

Location: crates/core/src/message.rs, crates/core/src/operations/

Problem: Operation messages (PutMsg, GetMsg, SubscribeMsg) carry contract state as Vec<u8>. Cloning an operation (per hop in relay chain) deep-copies the entire payload — full alloc + memcpy. For 500 KB state: ~500 µs + 500 KB alloc per clone.

Fix: Replace Vec<u8> with bytes::Bytes (already a dep). Bytes::clone() is an atomic refcount increment (~0.1 µs). Requires #[serde(with = "bytes::serde")] on fields.

Gain: Clone 500 KB: ~500 µs → ~0.1 µs (~5000×). Forward to 3 peers: 1.5 MB alloc → 3 refcount bumps.

Effort: High (architectural, days). Coordinate with in-flight PRs.

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2 — Congestion window busy-poll: replace with tokio::sync::Notify

Location: crates/core/src/transport/peer_connection/outbound_stream.rs:132-194

Problem: When BBR congestion window is full, send task busy-polls: 10× yield_now() (immediate re-queue), then 100 µs sleep, then 1 ms sleep. Under congestion at 1 Mbps: 7–30 ms/s CPU burned in polling.

Fix: Add tokio::sync::Notify to congestion controller. ACK path calls notify_one(), sender calls notified().await. Zero polling, instant wakeup.

Gain: Under congestion: 7–30 ms/s CPU → ~0 ms/s. Light load: unchanged.

Effort: Medium (2–3 hr). Wire notify_one() into ACK path. No new deps.

[github-actions]

🤖 Auto-labeled

Applied labels:

• T-enhancement (98% confidence)
• E-hard (90% confidence)
• A-networking (95% confidence)
• A-contracts (85% confidence)

Reasoning: The issue describes performance optimizations (replace Vec with bytes::Bytes and remove busy-poll with tokio::Notify) rather than a bug or new feature, so T-enhancement is appropriate. The change to message payload handling is architectural and will require careful coordination and days of work (E-hard). The fixes touch transport congestion control and peer connection send/ack paths (A-networking) and operation payloads/contract state serialization (A-contracts). The proposal is concrete but architectural and needs design/coordination before implementation, so S-needs-design is suggested.

Previous labels: none

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