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hakmem/core/hakmem_tiny_lifecycle.d

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Phase 12-1.1: EMPTY Slab Detection + Immediate Reuse (+13% improvement, 10.2M→11.5M ops/s) Implementation of Task-sensei Priority 1 recommendation: Add empty_mask to SuperSlab for immediate EMPTY slab detection and reuse, reducing Stage 3 (mmap) overhead. ## Changes ### 1. SuperSlab Structure (core/superslab/superslab_types.h) - Added `empty_mask` (uint32_t): Bitmap for EMPTY slabs (used==0) - Added `empty_count` (uint8_t): Quick check for EMPTY slab availability ### 2. EMPTY Detection API (core/box/ss_hot_cold_box.h) - Added `ss_is_slab_empty()`: Returns true if slab is completely EMPTY - Added `ss_mark_slab_empty()`: Marks slab as EMPTY (highest reuse priority) - Added `ss_clear_slab_empty()`: Removes EMPTY state when reactivated - Updated `ss_update_hot_cold_indices()`: Classify EMPTY/Hot/Cold slabs - Updated `ss_init_hot_cold()`: Initialize empty_mask/empty_count ### 3. Free Path Integration (core/box/free_local_box.c) - After `meta->used--`, check if `meta->used == 0` - If true, call `ss_mark_slab_empty()` to update empty_mask - Enables immediate EMPTY detection on every free operation ### 4. Shared Pool Stage 0.5 (core/hakmem_shared_pool.c) - New Stage 0.5 before Stage 1: Scan existing SuperSlabs for EMPTY slabs - Iterate over `g_super_reg_by_class[class_idx][]` (first 16 entries) - Check `ss->empty_count > 0` → scan `empty_mask` with `__builtin_ctz()` - Reuse EMPTY slab directly, avoiding Stage 3 (mmap/lock overhead) - ENV control: `HAKMEM_SS_EMPTY_REUSE=1` (default OFF for A/B testing) - ENV tunable: `HAKMEM_SS_EMPTY_SCAN_LIMIT=N` (default 16 SuperSlabs) ## Performance Results ``` Benchmark: Random Mixed 256B (100K iterations) OFF (default): 10.2M ops/s (baseline) ON (ENV=1): 11.5M ops/s (+13.0% improvement) ✅ ``` ## Expected Impact (from Task-sensei analysis) **Current bottleneck**: - Stage 1: 2-5% hit rate (free list broken) - Stage 2: 3-8% hit rate (rare UNUSED) - Stage 3: 87-95% hit rate (lock + mmap overhead) ← bottleneck **Expected with Phase 12-1.1**: - Stage 0.5: 20-40% hit rate (EMPTY scan) - Stage 1-2: 20-30% hit rate (combined) - Stage 3: 30-50% hit rate (significantly reduced) **Theoretical max**: 25M → 55-70M ops/s (+120-180%) ## Current Gap Analysis **Observed**: 11.5M ops/s (+13%) **Expected**: 55-70M ops/s (+120-180%) **Gap**: Performance regression or missing complementary optimizations Possible causes: 1. Phase 3d-C (25.1M→10.2M) regression - unrelated to this change 2. EMPTY scan overhead (16 SuperSlabs × empty_count check) 3. Missing Priority 2-5 optimizations (Lazy SS deallocation, etc.) 4. Stage 0.5 too conservative (scan_limit=16, should be higher?) ## Usage ```bash # Enable EMPTY reuse optimization export HAKMEM_SS_EMPTY_REUSE=1 # Optional: increase scan limit (trade-off: throughput vs latency) export HAKMEM_SS_EMPTY_SCAN_LIMIT=32 ./bench_random_mixed_hakmem 100000 256 42 ``` ## Next Steps **Priority 1-A**: Investigate Phase 3d-C→12-1.1 regression (25.1M→10.2M) **Priority 1-B**: Implement Phase 12-1.2 (Lazy SS deallocation) for complementary effect **Priority 1-C**: Profile Stage 0.5 overhead (scan_limit tuning) ## Files Modified Core implementation: - `core/superslab/superslab_types.h` - empty_mask/empty_count fields - `core/box/ss_hot_cold_box.h` - EMPTY detection/marking API - `core/box/free_local_box.c` - Free path EMPTY detection - `core/hakmem_shared_pool.c` - Stage 0.5 EMPTY scan Documentation: - `CURRENT_TASK.md` - Task-sensei investigation report --- 🎯 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com> Co-Authored-By: Task-sensei (investigation & design analysis)
2025-11-21 04:56:48 +09:00
core/hakmem_tiny_lifecycle.o: core/hakmem_tiny_lifecycle.c \
core/hakmem_tiny_lifecycle.h core/hakmem_tiny.h \
core/hakmem_build_flags.h core/hakmem_trace.h \
core/hakmem_tiny_mini_mag.h core/hakmem_tiny_superslab.h \
core/superslab/superslab_types.h core/hakmem_tiny_superslab_constants.h \
core/superslab/superslab_inline.h core/superslab/superslab_types.h \
core/tiny_debug_ring.h core/tiny_remote.h \
core/hakmem_tiny_superslab_constants.h core/hakmem_tiny_tls_ops.h \
core/hakmem_super_registry.h core/box/tiny_next_ptr_box.h \
core/hakmem_tiny_config.h core/tiny_nextptr.h \
core/hakmem_tiny_magazine.h core/hakmem_tiny_fastcache.inc.h \
core/tiny_tls.h core/tiny_tls_guard.h core/hakmem_tiny_tls_list.h \
core/box/ss_slab_meta_box.h core/box/../superslab/superslab_types.h
core/hakmem_tiny_lifecycle.h:
core/hakmem_tiny.h:
core/hakmem_build_flags.h:
core/hakmem_trace.h:
core/hakmem_tiny_mini_mag.h:
core/hakmem_tiny_superslab.h:
core/superslab/superslab_types.h:
core/hakmem_tiny_superslab_constants.h:
core/superslab/superslab_inline.h:
core/superslab/superslab_types.h:
core/tiny_debug_ring.h:
core/tiny_remote.h:
core/hakmem_tiny_superslab_constants.h:
core/hakmem_tiny_tls_ops.h:
core/hakmem_super_registry.h:
core/box/tiny_next_ptr_box.h:
core/hakmem_tiny_config.h:
core/tiny_nextptr.h:
core/hakmem_tiny_magazine.h:
core/hakmem_tiny_fastcache.inc.h:
core/tiny_tls.h:
core/tiny_tls_guard.h:
core/hakmem_tiny_tls_list.h:
core/box/ss_slab_meta_box.h:
core/box/../superslab/superslab_types.h:
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