Isolate I/O thread written client fields on a dedicated cache line

[abokhalill]

The reply append path explicitly supports appending while an I/O thread streams the same client, so during every in flight write job, the main thread updates net_output_bytes_curr_cmd while the owning I/O thread updates io_tracked_reply_len, nwritten and io_write_state a few bytes away on the same cache lines. Group every I/O thread written field on one _Alignas(CACHE_LINE_SIZE) line of its own, in the same spirit as #1179 did for used_memory_thread.

Signed off by: Yousef Ahmed yosefkhalil610@gmail.com

[coderabbitai]

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Reviewing files that changed from the base of the PR and between 3a10362 and 17d513f.

📒 Files selected for processing (1)

• src/unit/test_networking.cpp

🚧 Files skipped from review as they are similar to previous changes (1)

• src/unit/test_networking.cpp

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📝 Walkthrough

Walkthrough

The client structure now groups I/O-thread-owned fields into cache-line-aligned storage. Production and networking test client allocations use cache-line-aligned memory through updated allocation paths and a shared test helper.

Changes

Client cache alignment

Layer / File(s)	Summary
Aligned client structure layout src/server.h	The client layout reorganizes response and accounting fields, groups I/O-thread state and counters in an aligned region, moves io_last_written, and aligns client_list_node.
Aligned client allocation and test setup src/networking.c, src/unit/test_networking.cpp	createClient() and networking tests use cache-aligned client allocation, with tests routed through a shared zero-initializing helper.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change of isolating I/O-thread-written client fields on a dedicated cache line.
Description check	✅ Passed	The description is directly related to the cache-line layout change and the aligned test-client allocation updates.
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.

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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 `@src/server.h`:
- Around line 1379-1395: Update the client allocations in the networking unit
tests at the referenced construction sites to use
zmalloc_cache_aligned(sizeof(client)) instead of zmalloc/zcalloc. Ensure every
allocation of client objects is cache-line aligned to satisfy the
_Alignas(CACHE_LINE_SIZE) fields in the client definition, while preserving
existing initialization behavior.

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Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
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Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 298c617d-649d-4c4a-ac15-36bc3bb5407a

📥 Commits

Reviewing files that changed from the base of the PR and between 5c1fc15 and d14ee6e.

📒 Files selected for processing (2)

• src/networking.c
• src/server.h

[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 `@src/unit/test_networking.cpp`:
- Around line 140-146: Separate allocation from initialization in
src/unit/test_networking.cpp: rename the cache-aligned helper at lines 140-146
to a distinct allocator symbol, then update the initializing createTestClient()
at lines 536-537 to call that allocator instead of recursively calling itself;
preserve the existing client initialization behavior.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

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

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 426fa410-93f0-4eb2-9d46-7384e995a6a3

📥 Commits

Reviewing files that changed from the base of the PR and between d14ee6e and 3a10362.

📒 Files selected for processing (1)

• src/unit/test_networking.cpp

[abokhalill]

hey @madolson, would appreciate you taking a look at this once you have a cycle