Phase 5 E5-3: Candidate Analysis (All DEFERRED) + E5-4 Instructions
E5-3 Analysis Results:
- free_tiny_fast_cold (7.14%): DEFER - cold path, low ROI
- unified_cache_push (3.39%): DEFER - already optimized
- hakmem_env_snapshot_enabled (2.97%): DEFER - low headroom
Key Insight: perf self% is time-weighted, not frequency-weighted.
Cold paths appear hot but have low total impact.
Next: E5-4 (Malloc Tiny Direct Path)
- Apply E5-1 winning pattern to malloc side
- Target: tiny_alloc_gate_fast() gate tax elimination
- ENV gate: HAKMEM_MALLOC_TINY_DIRECT=0/1
Files added:
- docs/analysis/PHASE5_E5_3_ANALYSIS_AND_RECOMMENDATIONS.md
- docs/analysis/PHASE5_E5_4_MALLOC_TINY_DIRECT_NEXT_INSTRUCTIONS.md
- core/box/free_cold_shape_env_box.{h,c} (research box, not tested)
- core/box/free_cold_shape_stats_box.{h,c} (research box, not tested)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Moe Charm (CI)
@ -1,5 +1,68 @@
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# 本線タスク（現在）
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## 更新メモ（2025-12-14 Phase 5 E5-3 Analysis - Strategic Pivot）
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### Phase 5 E5-3: Candidate Analysis & Strategic Recommendations ⚠️ DEFER (2025-12-14)
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**Decision**: **DEFER all E5-3 candidates** (E5-3a/b/c). Pivot to E5-4 (Malloc Direct Path, E5-1 pattern replication).
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**Analysis**:
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- **E5-3a (free_tiny_fast_cold 7.14%)**: NO-GO (cold path, low frequency despite high self%)
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- **E5-3b (unified_cache_push 3.39%)**: MAYBE (already optimized, marginal ROI ~+1.0%)
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- **E5-3c (hakmem_env_snapshot_enabled 2.97%)**: NO-GO (E3-4 precedent shows -1.44% regression)
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**Key Insight**: **Profiler self% ≠ optimization opportunity**
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- Self% is time-weighted (samples during execution), not frequency-weighted
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- Cold paths appear hot due to expensive operations when hit, not total cost
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- E5-2 lesson: 3.35% self% → +0.45% NEUTRAL (branch overhead ≈ savings)
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**ROI Assessment**:
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| Candidate | Self% | Frequency | Expected Gain | Risk | Decision |
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|-----------|-------|-----------|---------------|------|----------|
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| E5-3a (cold path) | 7.14% | LOW | +0.5% | HIGH | NO-GO |
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| E5-3b (push) | 3.39% | HIGH | +1.0% | MEDIUM | DEFER |
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| E5-3c (env snapshot) | 2.97% | HIGH | -1.0% | HIGH | NO-GO |
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**Strategic Pivot**: Focus on **E5-1 Success Pattern** (wrapper-level deduplication)
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- E5-1 (Free Tiny Direct): +3.35% (GO) ✅
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- **Next**: E5-4 (Malloc Tiny Direct) - Apply E5-1 pattern to alloc side
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- **Expected**: +2-4% (similar to E5-1, based on malloc wrapper overhead)
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**Cumulative Status (Phase 5)**:
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- E4-1 (Free Wrapper Snapshot): +3.51% standalone
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- E4-2 (Malloc Wrapper Snapshot): +21.83% standalone
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- E4 Combined: +6.43% (from baseline with both OFF)
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- E5-1 (Free Tiny Direct): +3.35% (from E4 baseline)
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- E5-2 (Header Write-Once): +0.45% NEUTRAL (frozen)
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- **E5-3**: **DEFER** (analysis complete, no implementation/test)
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- **Total Phase 5**: ~+9-10% cumulative (E4+E5-1 promoted, E5-2 frozen, E5-3 deferred)
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**Implementation** (E5-3a research box, NOT TESTED):
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- Files created:
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- `core/box/free_cold_shape_env_box.{h,c}` (ENV gate, default OFF)
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- `core/box/free_cold_shape_stats_box.{h,c}` (stats counters)
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- `docs/analysis/PHASE5_E5_3_ANALYSIS_AND_RECOMMENDATIONS.md` (analysis)
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- Files modified:
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- `core/front/malloc_tiny_fast.h` (lines 418-437, cold path shape optimization)
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- Pattern: Early exit for LEGACY path (skip LARSON check when !use_tiny_heap)
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- **Status**: FROZEN (default OFF, pre-analysis shows NO-GO, not worth A/B testing)
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**Key Lessons**:
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1. **Profiler self% misleads** when frequency is low (cold path)
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2. **Micro-optimizations plateau** in already-optimized code (E5-2, E5-3b)
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3. **Branch hints are profile-dependent** (E3-4 failure, E5-3c risk)
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4. **Wrapper-level deduplication wins** (E4-1, E4-2, E5-1 pattern)
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**Next Steps**:
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- **E5-4 Design**: Malloc Tiny Direct Path (E5-1 pattern for alloc)
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- Target: malloc() wrapper overhead (~12.95% self% in E4 profile)
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- Method: Single size check → direct call to malloc_tiny_fast_for_class()
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- Expected: +2-4% (based on E5-1 precedent +3.35%)
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- Design doc: `docs/analysis/PHASE5_E5_4_MALLOC_TINY_DIRECT_DESIGN.md`
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- Next instructions: `docs/analysis/PHASE5_E5_4_MALLOC_TINY_DIRECT_NEXT_INSTRUCTIONS.md`
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---
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## 更新メモ（2025-12-14 Phase 5 E5-2 Complete - Header Write-Once）
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### Phase 5 E5-2: Header Write-Once Optimization ⚪ NEUTRAL (2025-12-14)
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@ -120,12 +183,15 @@
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**Next Steps**:
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- ✅ Promote: `HAKMEM_FREE_TINY_DIRECT=1` to `MIXED_TINYV3_C7_SAFE` preset
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- Next: E5-2 (Header Prefill at Refill, 2.59% target) or E5-3 (ENV Snapshot Shape, 2.57% target)
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- ✅ E5-2: NEUTRAL → FREEZE
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- ✅ E5-3: DEFER（ROI 低）
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- Next: **E5-4 (Malloc Tiny Direct)**（E5-1 パターンの alloc 側複製）
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- Design docs:
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- `docs/analysis/PHASE5_E5_1_FREE_TINY_DIRECT_1_DESIGN.md`
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- `docs/analysis/PHASE5_E5_1_FREE_TINY_DIRECT_1_AB_TEST_RESULTS.md`
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- `docs/analysis/PHASE5_E5_1_FREE_TINY_DIRECT_NEXT_INSTRUCTIONS.md`
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- `docs/analysis/PHASE5_E5_COMPREHENSIVE_ANALYSIS.md`
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- `docs/analysis/PHASE5_E5_4_MALLOC_TINY_DIRECT_NEXT_INSTRUCTIONS.md`
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---
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5
core/box/free_cold_shape_env_box.c
Normal file
5
core/box/free_cold_shape_env_box.c
Normal file
@ -0,0 +1,5 @@
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// free_cold_shape_env_box.c - Phase 5 E5-3a: Free Cold Path Shape Optimization
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#include "free_cold_shape_env_box.h"
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// Global gate state (-1: uninitialized, 0: OFF, 1: ON)
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int g_free_cold_shape = -1;
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57
core/box/free_cold_shape_env_box.h
Normal file
57
core/box/free_cold_shape_env_box.h
Normal file
@ -0,0 +1,57 @@
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// free_cold_shape_env_box.h - Phase 5 E5-3a: Free Cold Path Shape Optimization
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//
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// Purpose: Optimize free_tiny_fast_cold() branch structure for better prediction
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// Target: free_tiny_fast_cold (7.14% self% in Mixed workload)
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//
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// Hypothesis:
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// - Cold path has heavy branching overhead (route determination, LARSON check, ENV gates)
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// - MIXED workload: LARSON=0 and use_tiny_heap=0 are COMMON (not rare)
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// - Current branch hints assume LARSON/TinyHeap are rare, but profile shows otherwise
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// - Reordering branches + fixing hints can reduce mispredictions
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//
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// Strategy:
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// - Shape 1 (Optimized): Reorder branches to handle common LEGACY path first
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// - Check use_tiny_heap==0 FIRST (LIKELY in Mixed, ~90%+ of cold path)
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// - Short-circuit to LEGACY fallback when heap routing not needed
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// - Defer LARSON/cross-thread checks to only when needed (heap routes)
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// - Keep LARSON safety when needed (heap routes still do cross-thread check)
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//
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// Design:
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// - ENV: HAKMEM_FREE_COLD_SHAPE=0/1 (default: 0, research box)
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// - Shape 0 (baseline): Current structure (LARSON+heap check, then legacy)
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// - Shape 1 (optimized): use_tiny_heap==0 early exit, LARSON only for heap
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//
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// Expected Benefit:
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// - Reduce branch mispredictions in cold path (~7.14% self%)
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// - Target gain: +1-3% (if branch prediction is bottleneck)
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// - Conservative estimate: +0.5-1.5% (cold path is 7.14%, not dominant)
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//
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// Box Theory Compliance:
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// - L0: ENV gate (default 0)
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// - L1: Single boundary (free_tiny_fast_cold function)
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// - Rollback: ENV=0 reverts to baseline
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// - A/B testable: Same binary, ENV toggle
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#ifndef HAK_FREE_COLD_SHAPE_ENV_BOX_H
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#define HAK_FREE_COLD_SHAPE_ENV_BOX_H
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#include <stdlib.h>
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// Global gate state (defined in free_cold_shape_env_box.c)
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extern int g_free_cold_shape;
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// ENV gate: Check if optimized cold path shape is enabled
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// Default: 0 (baseline), set HAKMEM_FREE_COLD_SHAPE=1 for optimized shape
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static inline int free_cold_shape_enabled(void) {
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if (__builtin_expect(g_free_cold_shape == -1, 0)) {
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const char* e = getenv("HAKMEM_FREE_COLD_SHAPE");
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if (e && *e) {
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g_free_cold_shape = (*e == '1') ? 1 : 0;
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} else {
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g_free_cold_shape = 0; // default: OFF (research box)
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}
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}
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return g_free_cold_shape;
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}
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#endif // HAK_FREE_COLD_SHAPE_ENV_BOX_H
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29
core/box/free_cold_shape_stats_box.c
Normal file
29
core/box/free_cold_shape_stats_box.c
Normal file
@ -0,0 +1,29 @@
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// free_cold_shape_stats_box.c - Phase 5 E5-3a: Free Cold Shape Stats
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#include "free_cold_shape_stats_box.h"
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// Stats counters (global atomics)
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_Atomic uint64_t g_free_cold_shape_legacy_fast = 0;
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_Atomic uint64_t g_free_cold_shape_heap_path = 0;
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_Atomic uint64_t g_free_cold_shape_enabled_count = 0;
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void free_cold_shape_print_stats(void) {
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#if !HAKMEM_BUILD_RELEASE
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uint64_t legacy = atomic_load(&g_free_cold_shape_legacy_fast);
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uint64_t heap = atomic_load(&g_free_cold_shape_heap_path);
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uint64_t enabled = atomic_load(&g_free_cold_shape_enabled_count);
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uint64_t total = legacy + heap;
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if (total == 0) return; // No activity
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fprintf(stderr, "\n[FREE-COLD-SHAPE] Stats:\n");
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fprintf(stderr, " Shape enabled: %llu\n", (unsigned long long)enabled);
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fprintf(stderr, " LEGACY fast path: %llu (%.1f%%)\n",
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(unsigned long long)legacy,
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100.0 * legacy / total);
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fprintf(stderr, " Heap route path: %llu (%.1f%%)\n",
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(unsigned long long)heap,
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100.0 * heap / total);
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fprintf(stderr, " Total cold hits: %llu\n", (unsigned long long)total);
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fflush(stderr);
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#endif
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}
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34
core/box/free_cold_shape_stats_box.h
Normal file
34
core/box/free_cold_shape_stats_box.h
Normal file
@ -0,0 +1,34 @@
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// free_cold_shape_stats_box.h - Phase 5 E5-3a: Free Cold Shape Stats
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//
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// Purpose: Track cold path branch distributions
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// Metrics: legacy_fast_path, heap_path, shape_enabled
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#ifndef HAK_FREE_COLD_SHAPE_STATS_BOX_H
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#define HAK_FREE_COLD_SHAPE_STATS_BOX_H
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#include <stdint.h>
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#include <stdatomic.h>
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#include <stdio.h>
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// Forward declarations for HAKMEM_DEBUG_COUNTERS
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#ifndef HAKMEM_DEBUG_COUNTERS
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#define HAKMEM_DEBUG_COUNTERS 0
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#endif
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// Stats counters (global atomics, always compiled)
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extern _Atomic uint64_t g_free_cold_shape_legacy_fast; // Optimized: LEGACY path (no heap)
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extern _Atomic uint64_t g_free_cold_shape_heap_path; // Heap route path
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extern _Atomic uint64_t g_free_cold_shape_enabled_count; // Shape=1 hits
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// Increment macros (compile-out in release builds)
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#if HAKMEM_DEBUG_COUNTERS
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#define FREE_COLD_SHAPE_STAT_INC(name) \
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atomic_fetch_add_explicit(&g_free_cold_shape_##name, 1, memory_order_relaxed)
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#else
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#define FREE_COLD_SHAPE_STAT_INC(name) ((void)0)
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#endif
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// Print stats (implemented in free_cold_shape_stats_box.c)
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void free_cold_shape_print_stats(void);
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#endif // HAK_FREE_COLD_SHAPE_STATS_BOX_H
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@ -70,6 +70,8 @@
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#include "../box/tiny_metadata_cache_hot_box.h" // Phase 3 C2: Policy hot cache (metadata cache optimization)
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#include "../box/tiny_free_route_cache_env_box.h" // Phase 3 D1: Free path route cache
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#include "../box/hakmem_env_snapshot_box.h" // Phase 4 E1: ENV snapshot consolidation
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#include "../box/free_cold_shape_env_box.h" // Phase 5 E5-3a: Free cold path shape optimization
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#include "../box/free_cold_shape_stats_box.h" // Phase 5 E5-3a: Free cold shape stats
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// Helper: current thread id (low 32 bits) for owner check
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#ifndef TINY_SELF_U32_LOCAL_DEFINED
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@ -413,6 +415,28 @@ static int free_tiny_fast_cold(void* ptr, void* base, int class_idx)
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}
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#endif // !HAKMEM_BUILD_RELEASE
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// Phase 5 E5-3a: Optimized cold path shape
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// Strategy: Handle common LEGACY path first (use_tiny_heap==0 in Mixed ~90%+)
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// Defer expensive LARSON/cross-thread checks to only when heap routing needed
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static __thread int g_cold_shape = -1;
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if (__builtin_expect(g_cold_shape == -1, 0)) {
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g_cold_shape = free_cold_shape_enabled() ? 1 : 0;
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}
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if (g_cold_shape == 1) {
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// Optimized shape: Check use_tiny_heap FIRST
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if (__builtin_expect(!use_tiny_heap, 1)) {
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// Most common case in Mixed: LEGACY path, no heap routing
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// Skip LARSON/cross-thread check entirely (not needed for legacy)
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FREE_COLD_SHAPE_STAT_INC(legacy_fast);
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FREE_COLD_SHAPE_STAT_INC(enabled_count);
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goto legacy_fallback;
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}
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// Rare: heap routing needed, do full validation
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FREE_COLD_SHAPE_STAT_INC(heap_path);
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}
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// Baseline shape: LARSON check first (current behavior)
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// Cross-thread free detection (Larson MT crash fix, ENV gated) + TinyHeap free path
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{
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static __thread int g_larson_fix = -1;
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@ -467,7 +491,7 @@ static int free_tiny_fast_cold(void* ptr, void* base, int class_idx)
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}
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return 0; // remote push failed; fall back to normal path
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}
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// Same-thread + TinyHeap route → route-based free
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// Same-thread + TinyHeap route → route-based free
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if (__builtin_expect(use_tiny_heap, 0)) {
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FREE_TINY_FAST_HOTCOLD_STAT_INC(cold_tinyheap);
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switch (route) {
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@ -541,6 +565,7 @@ static int free_tiny_fast_cold(void* ptr, void* base, int class_idx)
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#endif
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// Phase REFACTOR-2: Legacy fallback (use unified helper)
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legacy_fallback:
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FREE_TINY_FAST_HOTCOLD_STAT_INC(cold_legacy_fallback);
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tiny_legacy_fallback_free_base(base, class_idx);
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return 1;
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@ -72,7 +72,7 @@ perf report --stdio --no-children
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```
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判断基準（self% ≥ 5%）:
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- `tiny_region_id_write_header` が依然 5% 以上 → **E5-2** 優先
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- `tiny_region_id_write_header` が依然 5% 以上 → **E5-2** は NEUTRAL で freeze 済み（次は E5-4 を優先）
|
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- `hakmem_env_snapshot_enabled` / `tiny_get_max_size` が 5% 付近まで上がる → **E5-3** 優先
|
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|
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---
|
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@ -83,4 +83,3 @@ perf report --stdio --no-children
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- 目標: `tiny_region_id_write_header` の hot path stores を減らす（A3 の “always_inline” は NO-GO 済み）
|
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- E5-3: `hakmem_env_snapshot_enabled()` の分岐形/配置を “enabled 前提” に寄せる
|
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- 目標: mispredict を避け、`malloc_tiny_fast.h` 内の繰り返し gate を軽くする
|
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|
||||
|
||||
231
docs/analysis/PHASE5_E5_3_ANALYSIS_AND_RECOMMENDATIONS.md
Normal file
231
docs/analysis/PHASE5_E5_3_ANALYSIS_AND_RECOMMENDATIONS.md
Normal file
@ -0,0 +1,231 @@
|
||||
# Phase 5 E5-3: Candidate Analysis and Strategic Recommendations
|
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|
||||
## Executive Summary
|
||||
|
||||
**Recommendation**: **DEFER E5-3 optimization**. Continue with established winning patterns (E5-1 style wrapper-level optimizations) rather than pursuing diminishing-returns micro-optimizations in profiler hot spots.
|
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|
||||
**Rationale**:
|
||||
- E5-2 (Header Write-Once, 3.35% self%) achieved only +0.45% NEUTRAL
|
||||
- E5-3 candidates (7.14%, 3.39%, 2.97% self%) have similar or worse ROI profiles
|
||||
- Profiler self% != optimization opportunity (time-weighted samples can mislead)
|
||||
- Cumulative gains from E4+E5-1 (~+9-10%) represent significant progress
|
||||
- Next phase should target higher-level structural opportunities
|
||||
|
||||
---
|
||||
|
||||
## E5-3 Candidate Analysis
|
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|
||||
### Context: Post-E5-2 Baseline
|
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- **E5-1 (Free Tiny Direct)**: +3.35% GO (adopted)
|
||||
- **E5-2 (Header Write-Once)**: +0.45% NEUTRAL (frozen as research box)
|
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- **New baseline**: 44.42M ops/s (Mixed, 20M iters, ws=400)
|
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|
||||
### Available Candidates (from perf profile)
|
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|
||||
| Candidate | Self% | Call Frequency | ROI Assessment |
|
||||
|-----------|-------|----------------|----------------|
|
||||
| free_tiny_fast_cold | 7.14% | LOW (cold path) | **NO-GO** |
|
||||
| unified_cache_push | 3.39% | HIGH (every free) | **MAYBE** |
|
||||
| hakmem_env_snapshot_enabled | 2.97% | HIGH (wrapper+gate) | **NO-GO** |
|
||||
|
||||
---
|
||||
|
||||
## Detailed Analysis
|
||||
|
||||
### E5-3a: free_tiny_fast_cold (7.14% self%) ❌ **NO-GO**
|
||||
|
||||
**Hypothesis**: Cold path branch structure optimization (route determination, LARSON check)
|
||||
|
||||
**Why NO-GO**:
|
||||
1. **Self% Misleading**: 7.14% is time-weighted, not frequency
|
||||
- Cold path is called RARELY (only when hot path misses)
|
||||
- High self% = expensive when hit, not = high total cost
|
||||
- Optimizing cold path has minimal impact on overall throughput
|
||||
|
||||
2. **Branch Prediction Already Optimized**:
|
||||
- Current implementation uses `__builtin_expect` hints
|
||||
- LARSON/heap checks are already marked UNLIKELY
|
||||
- Further branch reordering has marginal benefit (~0.1-0.5% at best)
|
||||
|
||||
3. **Similar to E5-2 Failure**:
|
||||
- E5-2 targeted 3.35% self%, gained only +0.45%
|
||||
- E5-3a targets 7.14% self% BUT lower frequency
|
||||
- Expected gain: +0.3-1.0% (< +1.0% GO threshold)
|
||||
|
||||
4. **Structural Issues**:
|
||||
- Goto-based early exit adds control flow complexity
|
||||
- Potential I-cache pollution (similar to Phase 1 A3 failure)
|
||||
- Safety risks (LARSON check bypass in optimized path)
|
||||
|
||||
**Conservative Estimate**: +0.5% ± 0.5% (NEUTRAL range)
|
||||
|
||||
**Decision**: **NO-GO / DEFER**
|
||||
|
||||
---
|
||||
|
||||
### E5-3b: unified_cache_push (3.39% self%) ⚠️ **MAYBE**
|
||||
|
||||
**Hypothesis**: Push operation overhead (TLS access, modulo arithmetic, bounds check)
|
||||
|
||||
**Why MAYBE**:
|
||||
1. **Frequency**: Called on EVERY free (high frequency)
|
||||
2. **Current Implementation**: Already highly optimized
|
||||
- Ring buffer with power-of-2 masking (no division)
|
||||
- Single TLS access (g_unified_cache[class_idx])
|
||||
- Minimal branch count (1-2 branches)
|
||||
|
||||
3. **Potential Optimizations**:
|
||||
- **Inline Expansion**: Force always_inline (may hurt I-cache)
|
||||
- **TLS Caching**: Cache g_unified_cache base pointer (adds TLS variable)
|
||||
- **Bounds Check Removal**: Assume capacity never changes (unsafe)
|
||||
|
||||
4. **Risk Assessment**:
|
||||
- **High risk**: unified_cache_push is already in critical path
|
||||
- **Low ROI**: 3.39% self% with limited optimization headroom
|
||||
- **Similar to E5-2**: Micro-optimization with marginal benefit
|
||||
|
||||
**Conservative Estimate**: +0.5-1.5% (borderline NEUTRAL/GO)
|
||||
|
||||
**Decision**: **DEFER** (pursue only if E5-1 pattern exhausted)
|
||||
|
||||
---
|
||||
|
||||
### E5-3c: hakmem_env_snapshot_enabled (2.97% self%) ❌ **NO-GO**
|
||||
|
||||
**Hypothesis**: Branch hint optimization (enabled=1 is常用 in MIXED)
|
||||
|
||||
**Why NO-GO**:
|
||||
1. **E3-4 Precedent**: Phase 4 E3-4 (ENV Constructor Init) **FAILED**
|
||||
- Attempted to eliminate lazy check overhead (3.22% self%)
|
||||
- Result: -1.44% regression (constructor mode added overhead)
|
||||
- Root cause: Branch predictor tuning is profile-dependent
|
||||
|
||||
2. **Branch Hint Contradiction**:
|
||||
- Default builds: enabled=0 → hint UNLIKELY is correct
|
||||
- MIXED preset: enabled=1 → hint UNLIKELY is WRONG
|
||||
- Changing hint helps MIXED but hurts default builds
|
||||
|
||||
3. **Optimization Space**: Already consolidated in E4-1 (E1)
|
||||
- ENV snapshot reduced 3 TLS reads → 1 TLS read
|
||||
- Remaining overhead is unavoidable (lazy init check)
|
||||
- Further optimization requires constructor init (E3-4 showed this fails)
|
||||
|
||||
**Conservative Estimate**: -1.0% to +0.5% (high regression risk)
|
||||
|
||||
**Decision**: **NO-GO** (proven failure in E3-4)
|
||||
|
||||
---
|
||||
|
||||
## Strategic Recommendations
|
||||
|
||||
### Priority 1: Exploit E5-1 Success Pattern ✅
|
||||
|
||||
**E5-1 Strategy (Free Tiny Direct)**:
|
||||
- **Target**: Wrapper-level overhead (deduplication)
|
||||
- **Method**: Single header check → direct call to free_tiny_fast()
|
||||
- **Result**: +3.35% (GO)
|
||||
|
||||
**Replicable Patterns**:
|
||||
1. **Malloc Tiny Direct**: Apply E5-1 pattern to malloc() side
|
||||
- Single size check → direct call to malloc_tiny_fast_for_class()
|
||||
- Eliminate: Size validation redundancy, ENV snapshot overhead
|
||||
- Expected: +2-4% (similar to E5-1)
|
||||
|
||||
2. **Alloc Gate Specialization**: Per-class fast paths
|
||||
- C0-C3: Direct to LEGACY (skip policy snapshot)
|
||||
- C4-C7: Route-specific fast paths
|
||||
- Expected: +1-3%
|
||||
|
||||
### Priority 2: Profile New Baseline
|
||||
|
||||
After E4+E5-1 adoption (~+9-10% cumulative):
|
||||
1. **Re-profile Mixed workload** (new bottlenecks may emerge)
|
||||
2. **Identify high-frequency, high-overhead** targets
|
||||
3. **Focus on deduplication/consolidation** (proven pattern)
|
||||
|
||||
### Priority 3: Avoid Diminishing Returns
|
||||
|
||||
**Red Flags** (E5-2, E5-3 lessons):
|
||||
- **Self% > 3%** but **low frequency** → misleading
|
||||
- **Micro-optimizations** in already-optimized code → marginal ROI
|
||||
- **Branch hint tuning** → profile-dependent, high regression risk
|
||||
- **Cold path optimization** → time-weighted ≠ frequency-weighted
|
||||
|
||||
**Green Flags** (E4-1, E4-2, E5-1 successes):
|
||||
- **Wrapper-level deduplication** → +3-6% per optimization
|
||||
- **TLS consolidation** → +2-4% per consolidation
|
||||
- **Direct path creation** → +2-4% per path
|
||||
- **Structural changes** (not micro-tuning) → higher ROI
|
||||
|
||||
---
|
||||
|
||||
## Lessons from Phase 5
|
||||
|
||||
### Wins (E4-1, E4-2, E5-1)
|
||||
1. **ENV Snapshot Consolidation** (E4-1): +3.51%
|
||||
- 3 TLS reads → 1 TLS read
|
||||
- Deduplication > micro-optimization
|
||||
|
||||
2. **Malloc Wrapper Snapshot** (E4-2): +21.83% standalone (+6.43% combined)
|
||||
- Function call elimination (tiny_get_max_size)
|
||||
- Pre-caching + TLS consolidation
|
||||
|
||||
3. **Free Tiny Direct** (E5-1): +3.35%
|
||||
- Single header check → direct call
|
||||
- Wrapper-level deduplication
|
||||
|
||||
**Common Pattern**: **Eliminate redundancy at architectural boundaries** (wrapper, gate, snapshot)
|
||||
|
||||
### Losses / Neutrals (E3-4, E5-2)
|
||||
1. **ENV Constructor Init** (E3-4): -1.44%
|
||||
- Constructor mode added overhead
|
||||
- Branch prediction is profile-dependent
|
||||
|
||||
2. **Header Write-Once** (E5-2): +0.45% NEUTRAL
|
||||
- Assumption incorrect (headers NOT redundant)
|
||||
- Branch overhead ≈ savings
|
||||
|
||||
**Common Pattern**: **Micro-optimizations in hot functions** have limited ROI when code is already optimized
|
||||
|
||||
---
|
||||
|
||||
## Conclusion
|
||||
|
||||
**E5-3 Recommendation**: **DEFER all three candidates**
|
||||
|
||||
**Rationale**:
|
||||
1. **E5-3a (cold path)**: Low frequency, high risk, estimated +0.5% NEUTRAL
|
||||
2. **E5-3b (push)**: Already optimized, marginal ROI, estimated +1.0% borderline
|
||||
3. **E5-3c (env snapshot)**: Proven failure (E3-4), estimated -1.0% NO-GO
|
||||
|
||||
**Next Steps**:
|
||||
1. ✅ **Promote E5-1** to `MIXED_TINYV3_C7_SAFE` preset (if not already done)
|
||||
2. ✅ **Profile new baseline** (E4+E5-1 ON) to find next high-ROI targets
|
||||
3. ✅ **Design E5-4**: Malloc Tiny Direct (E5-1 pattern applied to alloc side)
|
||||
- Expected: +2-4% based on E5-1 precedent
|
||||
- Lower risk than E5-3 candidates
|
||||
4. ✅ **Update roadmap**: Focus on wrapper-level optimizations, avoid diminishing returns
|
||||
|
||||
**Key Insight**: **Profiler self% is necessary but not sufficient** for optimization prioritization. Frequency, redundancy, and architectural seams matter more than raw self%.
|
||||
|
||||
---
|
||||
|
||||
## Appendix: Implementation Notes (E5-3a - Not Executed)
|
||||
|
||||
**Files Created** (research box, not tested):
|
||||
- `core/box/free_cold_shape_env_box.{h,c}` (ENV gate)
|
||||
- `core/box/free_cold_shape_stats_box.{h,c}` (stats counters)
|
||||
|
||||
**Integration Point**:
|
||||
- `core/front/malloc_tiny_fast.h` (lines 418-437, free_tiny_fast_cold)
|
||||
|
||||
**Decision**: **FROZEN** (default OFF, do not pursue A/B testing)
|
||||
|
||||
**Rationale**: Pre-analysis shows NO-GO (low frequency, high risk, marginal ROI < +1.0%)
|
||||
|
||||
---
|
||||
|
||||
**Date**: 2025-12-14
|
||||
**Phase**: 5 E5-3
|
||||
**Status**: Analysis Complete → **DEFER E5-3**, Proceed to E5-4 (Malloc Direct Path)
|
||||
**Cumulative**: E4+E5-1 = ~+9-10% (baseline: 44.42M ops/s Mixed)
|
||||
@ -0,0 +1,122 @@
|
||||
# Phase 5 E5-4: Malloc Tiny Direct Path（次の指示書）
|
||||
|
||||
## Status（2025-12-14 / E5-2 FREEZE 後）
|
||||
|
||||
- E5-1（Free Tiny Direct）は ✅ GO（+3.35%）
|
||||
- E5-2（Header refill write-once）は ⚪ NEUTRAL → FREEZE
|
||||
- E5-3（env shape 等）は **DEFER**
|
||||
- 次の芯: **E5-4（Malloc Tiny Direct）** = E5-1 の成功パターンを alloc 側へ複製
|
||||
|
||||
狙い:
|
||||
- `malloc()` wrapper から `tiny_alloc_gate_fast()` 呼び出しの “ゲート税” を削り、
|
||||
**wrapper → malloc_tiny_fast_for_class()** へ最短で入る。
|
||||
|
||||
前提:
|
||||
- “Tiny を使ってはいけない” モード（POOL_ONLY 等）を壊さない（= `g_tiny_route[]` は必ず尊重）。
|
||||
- fail-fast: 失敗したら既存経路へ即フォールバック。
|
||||
- 戻せる: ENV gate default OFF。
|
||||
|
||||
---
|
||||
|
||||
## Step 0: 対象ホットの確認（perf）
|
||||
|
||||
E4/E5-1 を ON にした baseline で確認:
|
||||
```sh
|
||||
HAKMEM_PROFILE=MIXED_TINYV3_C7_SAFE \
|
||||
perf record -F 99 -- ./bench_random_mixed_hakmem 20000000 400 1
|
||||
perf report --stdio --no-children
|
||||
```
|
||||
|
||||
狙いの目安:
|
||||
- `tiny_alloc_gate_fast` が self% **≥ 8%** なら E5-4 の ROI は高い
|
||||
|
||||
---
|
||||
|
||||
## Step 1: 箱の追加（ENV gate + optional stats）
|
||||
|
||||
### 1) ENV gate（必須）
|
||||
- 新規: `core/box/malloc_tiny_direct_env_box.h`
|
||||
- ENV: `HAKMEM_MALLOC_TINY_DIRECT=0/1`（default 0）
|
||||
- `static inline bool malloc_tiny_direct_enabled(void)` を提供
|
||||
|
||||
### 2) stats（任意、compile-out 推奨）
|
||||
- 新規: `core/box/malloc_tiny_direct_stats_box.h`
|
||||
- `direct_total`, `direct_hit`, `direct_miss`, `route_pool_only`, `class_oob`, `fast_null`
|
||||
- `HAKMEM_DEBUG_COUNTERS=0` で compile-out（観測税ゼロ）
|
||||
|
||||
Box Theory:
|
||||
- L0: ENV gate（戻せる）
|
||||
- L1: direct try（副作用ゼロ）
|
||||
- 見える化: カウンタのみ
|
||||
|
||||
---
|
||||
|
||||
## Step 2: wrapper へ統合（境界1箇所）
|
||||
|
||||
対象: `core/box/hak_wrappers.inc.h` の `malloc()` hot path（E4-2 snapshot の中）
|
||||
|
||||
やること:
|
||||
- 既存の
|
||||
- `size <= 256` → `tiny_alloc_gate_fast(size)`
|
||||
- `size <= tiny_get_max_size()` → `tiny_alloc_gate_fast(size)`
|
||||
を “direct try” に置換/前段追加する。
|
||||
|
||||
**Direct try の条件（安全最優先）**:
|
||||
1) `malloc_wrapper_env_snapshot_enabled()` が ON（E4-2 の経路内）
|
||||
2) `env->front_gate_unified` が true（Tiny front を使う前提）
|
||||
3) `size <= 256`（まず最頻だけ、範囲を狭く）
|
||||
4) `class_idx = hak_tiny_size_to_class(size)` が [0..7]
|
||||
5) `g_tiny_route[class_idx] != ROUTE_POOL_ONLY`（Tiny 禁止を尊重）
|
||||
|
||||
**Direct try の呼び出し**:
|
||||
- `void* p = malloc_tiny_fast_for_class(size, class_idx);`
|
||||
- `p != NULL` なら即 return
|
||||
- `p == NULL` なら既存ルートにフォールバック（TinyFirst/Refill失敗を許容）
|
||||
|
||||
重要:
|
||||
- `tiny_alloc_gate_fast()` の “診断/検証” は bypass されるので、
|
||||
debug ビルドでは direct try を **tiny_alloc_gate_diag_enabled()==0 のときだけ**に限定する（推奨）。
|
||||
|
||||
---
|
||||
|
||||
## Step 3: A/B テスト（同一バイナリ）
|
||||
|
||||
### A: baseline（E5-4 OFF）
|
||||
```sh
|
||||
HAKMEM_PROFILE=MIXED_TINYV3_C7_SAFE \
|
||||
HAKMEM_MALLOC_TINY_DIRECT=0 \
|
||||
./bench_random_mixed_hakmem 20000000 400 1
|
||||
```
|
||||
|
||||
### B: optimized（E5-4 ON）
|
||||
```sh
|
||||
HAKMEM_PROFILE=MIXED_TINYV3_C7_SAFE \
|
||||
HAKMEM_MALLOC_TINY_DIRECT=1 \
|
||||
./bench_random_mixed_hakmem 20000000 400 1
|
||||
```
|
||||
|
||||
判定（Mixed 10-run mean）:
|
||||
- GO: **+1.0% 以上**
|
||||
- ±1.0%: NEUTRAL → freeze
|
||||
- -1.0% 以下: NO-GO → freeze
|
||||
|
||||
追加で C6-heavy も 5-run だけ確認（回帰が無いこと）。
|
||||
|
||||
---
|
||||
|
||||
## Step 4: 健康診断（必須）
|
||||
|
||||
```sh
|
||||
scripts/verify_health_profiles.sh
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## Step 5: 昇格（GO のときだけ）
|
||||
|
||||
- `core/bench_profile.h`（`MIXED_TINYV3_C7_SAFE`）に:
|
||||
- `bench_setenv_default("HAKMEM_MALLOC_TINY_DIRECT", "1");`
|
||||
- `docs/analysis/ENV_PROFILE_PRESETS.md` に:
|
||||
- 効果、A/B、rollback（`HAKMEM_MALLOC_TINY_DIRECT=0`）を追記
|
||||
- `CURRENT_TASK.md` を更新
|
||||
|
||||
@ -1,6 +1,6 @@
|
||||
# Phase 5 E5: Post E4-Combined Next Instructions（次の指示書）
|
||||
|
||||
## Status（2025-12-14 / E4 Combined GO 後）
|
||||
## Status（2025-12-14 / E5-2 FREEZE 反映）
|
||||
|
||||
- Baseline（Mixed, 20M iters, ws=400）: **47.34M ops/s**（E4-1+E4-2 ON）
|
||||
- Hot spots（self%）:
|
||||
@ -15,6 +15,9 @@
|
||||
|
||||
Update:
|
||||
- E5-1（Free Tiny Direct Path）✅ GO（+3.35% mean / +3.36% median）→ 指示書: `docs/analysis/PHASE5_E5_1_FREE_TINY_DIRECT_NEXT_INSTRUCTIONS.md`
|
||||
- E5-2（Header write to refill boundary）⚪ NEUTRAL → FREEZE（追わない）
|
||||
- E5-3（env shape 等）DEFER → 次は E5-4（malloc 側 direct）
|
||||
- E5-4 指示書: `docs/analysis/PHASE5_E5_4_MALLOC_TINY_DIRECT_NEXT_INSTRUCTIONS.md`
|
||||
|
||||
---
|
||||
|
||||
@ -74,7 +77,15 @@ perf report --stdio --no-children --symbol free
|
||||
|
||||
---
|
||||
|
||||
## E5-2（優先B）: `tiny_region_id_write_header` を “毎回 alloc” から外す（refill 境界へ）
|
||||
## E5-2: Header write-once（⚪ NEUTRAL → FROZEN）
|
||||
|
||||
結論:
|
||||
- E5-2 は **NEUTRAL**（branch overhead ≈ savings）なので **freeze**。
|
||||
- 以後は追わず、次は E5-4 を優先する。
|
||||
|
||||
参照:
|
||||
- Design: `docs/analysis/PHASE5_E5_2_HEADER_REFILL_ONCE_DESIGN.md`
|
||||
- Results: `docs/analysis/PHASE5_E5_2_HEADER_REFILL_ONCE_AB_TEST_RESULTS.md`
|
||||
|
||||
### 仮説
|
||||
`tiny_region_id_write_header` は “正しいが高頻度”。
|
||||
@ -96,7 +107,14 @@ perf report --stdio --no-children --symbol free
|
||||
|
||||
---
|
||||
|
||||
## E5-3（優先C / 小パッチ）: `hakmem_env_snapshot_enabled()` の分岐形を “enabled 前提” に寄せる
|
||||
## E5-4（次の芯）: Malloc Tiny Direct（E5-1 の alloc 側複製）
|
||||
|
||||
指示書:
|
||||
- `docs/analysis/PHASE5_E5_4_MALLOC_TINY_DIRECT_NEXT_INSTRUCTIONS.md`
|
||||
|
||||
---
|
||||
|
||||
## E5-3（DEFER）: `hakmem_env_snapshot_enabled()` の分岐形を “enabled 前提” に寄せる
|
||||
|
||||
### 背景
|
||||
`MIXED_TINYV3_C7_SAFE` では `HAKMEM_ENV_SNAPSHOT=1` が常用になったため、
|
||||
|
||||
@ -73,3 +73,4 @@ scripts/verify_health_profiles.sh
|
||||
- E4 合算 A/B: `docs/analysis/PHASE5_E4_COMBINED_AB_TEST_NEXT_INSTRUCTIONS.md`
|
||||
- E5 次の芯: `docs/analysis/PHASE5_E5_NEXT_INSTRUCTIONS.md`
|
||||
- E5-1 昇格: `docs/analysis/PHASE5_E5_1_FREE_TINY_DIRECT_NEXT_INSTRUCTIONS.md`
|
||||
- E5-4 次: `docs/analysis/PHASE5_E5_4_MALLOC_TINY_DIRECT_NEXT_INSTRUCTIONS.md`
|
||||
|
||||
Reference in New Issue
Block a user