36 lines
1.1 KiB
Markdown
36 lines
1.1 KiB
Markdown
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C7 Free Hotpath (design memo)
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=============================
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Goals
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-----
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- Flatten the dominant C7 free path to minimise branches and helper hops.
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- Keep safety checks boxed; keep hot lane minimal.
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Current typical path (C7)
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-------------------------
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1. size→class LUT → `class_idx = 7`.
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2. free gate / route box decides Tiny vs Pool.
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3. Tiny free fast v2:
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- Policy/env checks,
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- TLS SLL push,
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- Warm/UC interaction as needed.
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4. Multiple helper calls along the way (gate, policy, sll push).
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Target hot lane
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---------------
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1. Single policy snapshot for C7 (warm/page/tls on).
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2. Straight to TLS SLL push with minimal bookkeeping.
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3. Optional UC/Warm stats only in sampled mode.
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4. Rare branches (remote/free-list edge cases) stay in boxed slow path.
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Ideas to explore
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----------------
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- Add `hak_tiny_free_fast_v2_c7()` inline used when `class_idx==7`.
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- Fold gate/policy reads into one branch per free call.
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- Keep TLS SLL push inline, push remote/cross-thread cases behind unlikely branches.
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Validation
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----------
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- Compare C7-only ops/s before/after.
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- Ensure remote/free-list invariants stay enforced in the slow path.
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