Files
hakmem/docs/paper/ACE_ALLOC_NOTES.md
Moe Charm (CI) 0546454168 WIP: Add TLS SLL validation and SuperSlab registry fallback
ChatGPT's diagnostic changes to address TLS_SLL_HDR_RESET issue.
Current status: Partial mitigation, but root cause remains.

Changes Applied:
1. SuperSlab Registry Fallback (hakmem_super_registry.h)
   - Added legacy table probe when hash map lookup misses
   - Prevents NULL returns for valid SuperSlabs during initialization
   - Status:  Works but may hide underlying registration issues

2. TLS SLL Push Validation (tls_sll_box.h)
   - Reject push if SuperSlab lookup returns NULL
   - Reject push if class_idx mismatch detected
   - Added [TLS_SLL_PUSH_NO_SS] diagnostic message
   - Status:  Prevents list corruption (defensive)

3. SuperSlab Allocation Class Fix (superslab_allocate.c)
   - Pass actual class_idx to sp_internal_allocate_superslab
   - Prevents dummy class=8 causing OOB access
   - Status:  Root cause fix for allocation path

4. Debug Output Additions
   - First 256 push/pop operations traced
   - First 4 mismatches logged with details
   - SuperSlab registration state logged
   - Status:  Diagnostic tool (not a fix)

5. TLS Hint Box Removed
   - Deleted ss_tls_hint_box.{c,h} (Phase 1 optimization)
   - Simplified to focus on stability first
   - Status:  Can be re-added after root cause fixed

Current Problem (REMAINS UNSOLVED):
- [TLS_SLL_HDR_RESET] still occurs after ~60 seconds of sh8bench
- Pointer is 16 bytes offset from expected (class 1 → class 2 boundary)
- hak_super_lookup returns NULL for that pointer
- Suggests: Use-After-Free, Double-Free, or pointer arithmetic error

Root Cause Analysis:
- Pattern: Pointer offset by +16 (one class 1 stride)
- Timing: Cumulative problem (appears after 60s, not immediately)
- Location: Header corruption detected during TLS SLL pop

Remaining Issues:
⚠️ Registry fallback is defensive (may hide registration bugs)
⚠️ Push validation prevents symptoms but not root cause
⚠️ 16-byte pointer offset source unidentified

Next Steps for Investigation:
1. Full pointer arithmetic audit (Magazine ⇔ TLS SLL paths)
2. Enhanced logging at HDR_RESET point:
   - Expected vs actual pointer value
   - Pointer provenance (where it came from)
   - Allocation trace for that block
3. Verify Headerless flag is OFF throughout build
4. Check for double-offset application in conversions

Technical Assessment:
- 60% root cause fixes (allocation class, validation)
- 40% defensive mitigation (registry fallback, push rejection)

Performance Impact:
- Registry fallback: +10-30 cycles on cold path (negligible)
- Push validation: +5-10 cycles per push (acceptable)
- Overall: < 2% performance impact estimated

Related Issues:
- Phase 1 TLS Hint Box removed temporarily
- Phase 2 Headerless blocked until stability achieved

🤖 Generated with Claude Code (https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
2025-12-03 20:42:28 +09:00

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Raw Blame History

ACE-Alloc Paper Notes (Scratchpad)

このファイルは、ACE / 学習機能まわりの実験メモ・アイデア・ストーリー断片を雑に書き溜めるためのスクラッチパッドです。 後で docs/paper/ACE-Alloc/main.md にまとめ直す前提の「素材置き場」として使います。

アイデアメモ(例)

  • Tiny Headerless + Superslab + ACE の組み合わせで:

    • Headerless: free パスでの class 決定を Superslab/region に移し、per-object header を除去。
    • ACE Controller: Mid/Large の TLS CAP / drain をオフパスで学習。
    • CAP Learner: Mid/Large の CAP / W_MAX をヒット率ベースで調整。
    • → 「ヘッダレス+学習」で、密度と性能を両立できるか?
  • 学習の「層ごとの役割分担」:

    • L0 Tiny: 原則固定(学習対象外)。ただし Observer だけ Tiny を見る。
    • L1 ACE: キャッシュ構成CAP / drain / bundleを学習。
    • L2 ELO+Evolution: しきい値・戦略の切り替えを学習。
    • → Box Theory 的には、学習そのものも「上層の箱」として Tiny/SuperSlab から分離されている。

実験ネタ候補

  • ACE ON/OFF が Tiny Headerless の性能・安定性に与える影響。
  • HAKMEM_MODE=balanced vs learning vs research での学習挙動の違い。
  • LD_PRELOAD モードで学習機能をどこまで有効にできるか(安全性とのトレードオフ)。