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5cc1f93622
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Phase 13-A Step 1: TinyHeapV2 NO-REFILL L0 cache implementation
Implement TinyHeapV2 as a minimal "lucky hit" L0 cache that avoids
circular dependency with FastCache by eliminating self-refill.
Key Changes:
- New: core/front/tiny_heap_v2.h - NO-REFILL L0 cache implementation
- tiny_heap_v2_alloc(): Pop from magazine if available, else return NULL
- tiny_heap_v2_refill_mag(): No-op stub (no backend refill)
- ENV: HAKMEM_TINY_HEAP_V2=1 to enable
- ENV: HAKMEM_TINY_HEAP_V2_CLASS_MASK=bitmask (C0-C3 control)
- ENV: HAKMEM_TINY_HEAP_V2_STATS=1 to print statistics
- Modified: core/hakmem_tiny_alloc_new.inc - Add TinyHeapV2 hook
- Hook at entry point (after class_idx calculation)
- Fallback to existing front if TinyHeapV2 returns NULL
- Modified: core/hakmem_tiny_alloc.inc - Add hook for legacy path
- Modified: core/hakmem_tiny.c - Add TLS variables and stats wrapper
- TinyHeapV2Mag: Per-class magazine (capacity=16)
- TinyHeapV2Stats: Per-class counters (alloc_calls, mag_hits, etc.)
- tiny_heap_v2_print_stats(): Statistics output at exit
- New: TINY_HEAP_V2_TASK_SPEC.md - Phase 13 specification
Root Cause Fixed:
- BEFORE: TinyHeapV2 refilled from FastCache → circular dependency
- TinyHeapV2 intercepted all allocs → FastCache never populated
- Result: 100% backend OOM, 0% hit rate, 99% slowdown
- AFTER: TinyHeapV2 is passive L0 cache (no refill)
- Magazine empty → return NULL → existing front handles it
- Result: 0% overhead, stable baseline performance
A/B Test Results (100K iterations, fixed-size bench):
- C1 (8B): Baseline 9,688 ops/s → HeapV2 ON 9,762 ops/s (+0.76%)
- C2 (16B): Baseline 9,804 ops/s → HeapV2 ON 9,845 ops/s (+0.42%)
- C3 (32B): Baseline 9,840 ops/s → HeapV2 ON 9,814 ops/s (-0.26%)
- All within noise range: NO PERFORMANCE REGRESSION ✅
Statistics (HeapV2 ON, C1-C3):
- alloc_calls: 200K (hook works correctly)
- mag_hits: 0 (0%) - Magazine empty as expected
- refill_calls: 0 - No refill executed (circular dependency avoided)
- backend_oom: 0 - No backend access
Next Steps (Phase 13-A Step 2):
- Implement magazine supply strategy (from existing front or free path)
- Goal: Populate magazine with "leftover" blocks from existing pipeline
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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2025-11-15 01:42:57 +09:00 |
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