⚡ Bolt: Batch producer wakeups outside spinlock

[maxugly]

💡 What: Batched netif_wake_queue outside the spinlock in nata_poll.
🎯 Why: Reduces lock contention on priv->lock by avoiding repeated producer queue wakeups within the short spinlock during NAPI receive dequeues.
📊 Impact: Reduces overhead in the high-frequency polling hotpath, lowering latency and improving throughput.
🔬 Measurement: Can be verified by running sudo ./scripts/nata-bench-once.sh and observing iperf3 UDP/TCP throughput or checking natactl status interrupts/drops.

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PR created automatically by Jules for task 6251807817317983420 started by @maxugly

Summary by CodeRabbit

• Performance Improvements
  • Improved network packet processing efficiency by batching queue wakeups during polling.
  • Reduced unnecessary repeated wakeups while processing packets, helping minimize locking overhead.

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[coderabbitai]

📝 Walkthrough

Walkthrough

nata_poll no longer wakes the peer TX queue after each RX dequeue. It performs one wakeup after a non-empty RX batch and outside the spinlock. The learning entry documents this pattern.

Changes

NAPI wakeup batching

Layer / File(s)	Summary
Batch and defer peer TX wakeup .jules/bolt.md, module/nata_net.c	nata_poll removes per-dequeue wakeups from the locked RX path and performs one peer TX queue wakeup after a non-empty batch. The learning entry documents the batching guidance.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Possibly related PRs

• maxugly/nata#31: Implements the same peer TX wakeup batching and deferral in nata_poll.
• maxugly/nata#33: Modifies nata_poll to batch the peer TX queue wakeup outside the spinlock.
• maxugly/nata#35: Batches nata_wake_tx_peer calls after RX processing.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes batching producer wakeups outside the spinlock, which is the main change.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch bolt-batch-producer-wakeups-6251807817317983420

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@module/nata_net.c`:
- Around line 49-51: Update the RX consumption flow around sim_rx_dequeue() to
track consumed slots independently of delivered packet count, including ret < 0
cases that clear valid and advance the tail. Call nata_wake_tx_peer() whenever
any slot was freed, while retaining work for packet-delivery accounting.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 6f47c41f-e0f3-4a97-87bc-ec59bf5be297

📥 Commits

Reviewing files that changed from the base of the PR and between 6d5b3ed and 7077f18.

📒 Files selected for processing (2)

• .jules/bolt.md
• module/nata_net.c

[coderabbitai]

🩺 Stability & Availability | 🟠 Major | ⚡ Quick win

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
set -euo pipefail

# Verify the dequeue return contract and all queue stop/wake paths.
rg -n -C 10 '\bsim_rx_dequeue\s*\(|\bnetif_(stop|wake)_queue\s*\(|\bcheck_tx_full\s*\(' module

Repository: maxugly/nata

Length of output: 7908

---

🏁 Script executed:

#!/bin/bash
set -euo pipefail

printf 'nata_net.c context:\n'
cat -n module/nata_net.c | sed -n '24,60p'

printf '\nsim_rx_dequeue implementation:\n'
cat -n module/nata_blk.c | sed -n '184,280p'

printf '\nTX enqueue/stop contexts with netif_queue_stopped/queue wake:\n'
rg -n -C 5 'netif_queue_stopped|netif_wake_queue|netif_stop_queue|sim_tx_packet|check_tx_full' module

Repository: maxugly/nata

Length of output: 11513

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Wake the producer after every consumed RX slot.

sim_rx_dequeue() returns <0 after clearing valid and advancing the tail. The ret < 0 branch continues without incrementing work, so a full stopped TX queue back on the same ring does not get woken. Track freed/consumed slots separately and call nata_wake_tx_peer() whenever a slot was freed, not only when packets were delivered.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@module/nata_net.c` around lines 49 - 51, Update the RX consumption flow
around sim_rx_dequeue() to track consumed slots independently of delivered
packet count, including ret < 0 cases that clear valid and advance the tail.
Call nata_wake_tx_peer() whenever any slot was freed, while retaining work for
packet-delivery accounting.

Source: Coding guidelines