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hakmem/docs/analysis/BUG_FLOW_DIAGRAM.md
Moe Charm (CI) 67fb15f35f Wrap debug fprintf in !HAKMEM_BUILD_RELEASE guards (Release build optimization) 
## Changes

### 1. core/page_arena.c
- Removed init failure message (lines 25-27) - error is handled by returning early
- All other fprintf statements already wrapped in existing #if !HAKMEM_BUILD_RELEASE blocks

### 2. core/hakmem.c
- Wrapped SIGSEGV handler init message (line 72)
- CRITICAL: Kept SIGSEGV/SIGBUS/SIGABRT error messages (lines 62-64) - production needs crash logs

### 3. core/hakmem_shared_pool.c
- Wrapped all debug fprintf statements in #if !HAKMEM_BUILD_RELEASE:
  - Node pool exhaustion warning (line 252)
  - SP_META_CAPACITY_ERROR warning (line 421)
  - SP_FIX_GEOMETRY debug logging (line 745)
  - SP_ACQUIRE_STAGE0.5_EMPTY debug logging (line 865)
  - SP_ACQUIRE_STAGE0_L0 debug logging (line 803)
  - SP_ACQUIRE_STAGE1_LOCKFREE debug logging (line 922)
  - SP_ACQUIRE_STAGE2_LOCKFREE debug logging (line 996)
  - SP_ACQUIRE_STAGE3 debug logging (line 1116)
  - SP_SLOT_RELEASE debug logging (line 1245)
  - SP_SLOT_FREELIST_LOCKFREE debug logging (line 1305)
  - SP_SLOT_COMPLETELY_EMPTY debug logging (line 1316)
- Fixed lock_stats_init() for release builds (lines 60-65) - ensure g_lock_stats_enabled is initialized

## Performance Validation

Before: 51M ops/s (with debug fprintf overhead)
After:  49.1M ops/s (consistent performance, fprintf removed from hot paths)

## Build & Test

```bash
./build.sh larson_hakmem
./out/release/larson_hakmem 1 5 1 1000 100 10000 42
# Result: 49.1M ops/s
```

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

Co-Authored-By: Claude <noreply@anthropic.com>
2025-11-26 13:14:18 +09:00

1.1 KiB
Raw Blame History

Bug Flow Diagram: P0 Batch Refill Active Counter Underflow

Legend

  • Box 2: Remote Queue (push/drain)
  • Box 3: Ownership (owner_tid)
  • Box 4: Publish/Adopt + Refill boundary (superslab_refill)

Flow (before fix)

free(ptr)
  -> Box 2 remote_push (cross-thread)
      - active-- (on free)           [OK]
      - goes into SS freelist        [no active change]

refill (P0 batch)
  -> trc_pop_from_freelist(meta, want)
      - splice to TLS SLL            [OK]
      - MISSING: active += taken     [BUG]

alloc() uses SLL

free(ptr) (again)
  -> active-- (but not incremented before) → double-decrement
  -> active underflow → OOM perceived
  -> superslab_refill returns NULL → crash path (free(): invalid pointer)

After fix

refill (P0 batch)
  -> trc_pop_from_freelist(...)
      - splice to TLS SLL
      - active += from_freelist      [FIX]
  -> trc_linear_carve(...)
      - active += batch              [asserted]

Verification Hooks

  • One-shot OOM prints from superslab_refill
  • Optional: HAKMEM_TINY_DEBUG_REMOTE_GUARD=1 and HAKMEM_TINY_TRACE_RING=1