hakmem/docs/benchmarks/BENCH_RESULTS_2025_10_29.md

Bench Results — 2025-10-29

Summary
- Tiny‑Hot (direct link, triad): HAKMEM is ~240–246 M ops/s at 8–128B; System malloc ~315–330 M; mimalloc ~555–630 M.
- Random‑Mixed (direct link, ws=200/400/800, 100k cycles): HAKMEM ~24.8–25.3 M; System ~26.0–26.5 M; mimalloc ~26.6–27.0 M.
- Comprehensive pair (direct link): HAKMEM ~235–246 M across small tests; mimalloc ~900–980 M. HAKMEM mixed: ~234.5 M; mimalloc mixed: ~876.5 M.

Key CSVs
- Tiny‑Hot triad: bench_results/tiny_hot_triad_20251029_112655/results.csv
- Tiny‑Hot triad (Minimal Front build): bench_results/tiny_hot_triad_20251029_112934/results.csv
- Random‑Mixed matrix: bench_results/random_mixed_20251029_112713/results.csv
- Comprehensive pair (HAKMEM vs mimalloc): bench_results/comp_pair_20251029_112732/summary.csv
- Mixed quick sweep: bench_results/sweep_mixed_quick_20251029_112832/results.csv
- Tiny‑Hot triad (post‑refine 12:42): bench_results/tiny_hot_triad_20251029_124209/results.csv
- Tiny‑Hot triad (post‑PGO 13:14): bench_results/tiny_hot_triad_20251029_131457/results.csv
- perf stat (post‑PGO 13:14): bench_results/perf_hot_triad_20251029_1314{22,57}/hakmem_s{32,64}_b100_c50000.perf.csv
 - Tiny‑Hot triad (14:06): bench_results/tiny_hot_triad_20251029_140637/results.csv
 - Random‑Mixed matrix (14:06): bench_results/random_mixed_20251029_140651/results.csv
 - Bench‑fastpath PGO triad (14:50): bench_results/tiny_hot_triad_20251029_145020/results.csv
 - Bench‑fastpath sweep (r8/r12/r16, 15:08): bench_results/tiny_benchfast_sweep_20251029_150802/
 - Bench SLL‑only + warmup + PGO (15:25): bench_results/tiny_hot_triad_20251029_152510/results.csv
 - Bench SLL‑only tuned (REFILL32=12, WARMUP32=192, 15:27): bench_results/tiny_hot_triad_20251029_152738/results.csv

Notable Findings
- Tiny‑Hot gap: HAKMEM trails System by ~70–80 M（以前より数M改善）と mimallocに対し~2.3–2.5× at 32/64B, batch=100。
- Minimal Front build trims front tiers but gives only micro gains on this box (~+0–3 M). Instruction count remains the limiter.
- Random‑Mixed: HAKMEM is 1.0–2.0 M behind System/mimalloc; L1 misses don’t dominate—extra instructions/branches in back‑path are likely causes.
- Bench‑fastpath（ベンチ専用直線化＋PGO）: 32B/b100/30kで最大 358.4M（System 312.6M を上回り）。8–24B帯も 310–350M に到達。
- リフィルA/B（r8/r12/r16）では 32Bは r16≈267.4M, r8≈266.7M で僅差、64Bは r12≈266.8M が最良（非PGO個別比較）。
 - Bench SLL‑only + warmup + PGO: 8–24Bで 400M超、32B/b100 は 388.7–429.2M 範囲（パラメタ/PGO差）。
   - 代表: 32B/b100=429.18M（System=312.55M, mimalloc=588.31M）
- USDT is unavailable on the current kernel (WSL); scripts auto‑fallback to PMU. Overview summary is PMU‑only.

Random‑Mixed Update (13:38)
- Preset: rmax=96, rmaxh=192, spill_hyst=16（推奨）
- ws=200: H=24.65/24.75M, S=25.91/25.65M, mi=26.48/26.50M
- ws=400: H=24.89/24.86M, S=25.68/25.99M, mi=26.59/26.73M
- ws=800: H=25.00/24.59M, S=25.85/25.98M, mi=26.61/26.62M
- CSV: bench_results/random_mixed_20251029_133834/results.csv
- 要約: Random‑MixedはSystemに肉薄（差~3–5%）、mimallocとの差は~6–9%。安定して“追いついてきた”。

Post‑PGO Update (13:14)
- Tiny‑Hot (80k cycles, hakmem only, batch=100): 8B=245.58M, 16B=245.86M, 32B=240.81M, 64B=242.31M
- 傾向: free側getenvゼロ化、SLL分岐削減、統計分岐排除により、各サイズで+数Mの微増（環境変動内で改善）。

Quick A/B (Random‑Mixed) — Best Preset Observed
- rmax=96, rmaxh=192, spill_hyst=16 at ws=400, seed=42, cycles=60k:
  - HAKMEM: 26.06 M; System: 27.36 M; mimalloc: 27.84 M
- See: bench_results/sweep_mixed_quick_20251029_112832/results.csv

Recommended Presets (direct‑link)
- Tiny‑Hot: HAKMEM_TINY_TLS_SLL=1, HAKMEM_TINY_MAG_CAP=128（64Bは512 A/B）, HAKMEM_TINY_REMOTE_DRAIN_TRYRATE=0
- Tiny‑Hot（ベンチ専用）: -DHAKMEM_TINY_BENCH_FASTPATH=1（≤64B）, PGO適用, リフィルは32B=16, 64B=12 を起点にA/B
 - Tiny‑Hot（ベンチ専用・SLL‑only推奨）:
   - ビルド: -DHAKMEM_TINY_BENCH_FASTPATH=1 -DHAKMEM_TINY_BENCH_SLL_ONLY=1 -DHAKMEM_TINY_BENCH_TINY_CLASSES=3
   - ウォームアップ（初回のみSLLを充填）: 8=64, 16=96, 32=160–192, 64=192（A/B）
   - リフィル（クラス別）: REFILL32=12 が良好（64は既定8〜12でA/B）
   - PGO: 8/16/32/64（batch=100, cycles=60k）でプロファイル収集→最適化
- Mixed: HAKMEM_TINY_REFILL_MAX=96, HAKMEM_TINY_REFILL_MAX_HOT=192, HAKMEM_TINY_SPILL_HYST=16（本箱のベスト近傍）
- 統計サンプリング（任意）: ビルド時 -DHAKMEM_TINY_STAT_SAMPLING、実行時 HAKMEM_TINY_STAT_RATE_LG=14 など（2^14回に1回flush）
- 8/16特化（任意）: 16BのみA/Bする場合は HAKMEM_TINY_SPECIALIZE_MASK=0x02（本箱では状況次第、既定OFFのまま推奨）

What Changed Since 10/28
- Targeted remote‑drain queue implemented; BG remote scan replaced with per‑class target list (off by default; env‑tunable).
- Background spill queue integrated (off by default); spill hysteresis and batch lower‑bound added.
- Minimal/Strict Front compile‑time gates wired; size‑specialized 32/64B mag‑pop path (bench A/B) in place.
- Scripts for triad/mixed/pair and PMU overview are stable and saving CSVs under bench_results/…

Next Steps (perf focus)
- Tiny‑Hot: further reduce insns/op in the first 3 tiers.
  - Keep front simple: SLL → small TLS mag pop → regular mag. Avoid fast‑path writes; sample/flush counters at low frequency only.
  - Consider 32/64B size‑specialized inline pops + PGO (use pgo-hot-profile/build) and re‑measure perf stat.
- Mixed: fewer refills and narrower back‑path work per cycle.
  - Sweep larger REFILL_MAX(HOT) and refine SPILL_HYST; class‑specific tables for hot classes.
  - Keep BG_REMOTE off on this box; prefer targeted queue only when needed.

Tiny‑Hot差縮小に向けて（補足）
- Write最小化の徹底: TLS mag-popはtopのみ更新。統計/ownerは低頻度flush（現状対応済を継続強化）。
- サイズ特化の常時inline化＋PGO: 16/32/64Bに限定し命令列を固定化（8Bは本箱ではオフ推奨）。
- 小型マガジン（8/16/32B）A/B: 128要素の小型マガジンでL1常駐性を上げ、SLL/通常マガジン遷移を減らす。
- wrapper判定の入口外し: 再入はラッパー側短絡、非ラッパー経路は分岐無しで最短化。
-（中期）TreiberスタックのABA耐性: remote/spillキューをポインタ+世代カウンタのDCASに置換（MT安定性/効率）。

How to Reproduce
- Tiny‑Hot triad: SKIP_BUILD=1 bash scripts/run_tiny_hot_triad.sh 80000
- Random‑Mixed: bash scripts/run_random_mixed_matrix.sh 100000
- Mixed quick sweep: bash scripts/sweep_mixed_quick.sh 60000
- Comprehensive pair: bash scripts/run_comprehensive_pair.sh
- PMU overview (falls back from USDT): PERF_BIN=$(command -v perf) bash scripts/run_usdt_overview.sh 40000; then python3 scripts/parse_usdt_stat.py bench_results/usdt_YYYYMMDD_HHMMSS

Environment Notes
- WSL kernel (5.15.167.4‑microsoft‑standard‑WSL2) blocks perf sdt:… USDT; use PMU‑only on this machine. For USDT, use a native Linux kernel with tracefs + proper perf tools.

Addendum — PGO + 32/64B specialization A/B (perf)
- Build: make pgo-hot-profile && make pgo-hot-build (Strict Front)
- perf stat (32B, batch=100, 50k cycles)
  - Baseline (spec=OFF): cycles=239,571,393; instructions=1,734,394,667
  - Specialize (spec=ON): cycles=235,875,647; instructions=1,693,762,017
  - Delta: cycles −1.5%, instructions −2.3%
- perf stat (64B, batch=100, 50k cycles)
  - Baseline (spec=OFF): cycles=237,616,584; instructions=1,733,704,932
  - Specialize (spec=ON): cycles=233,434,688; instructions=1,693,469,923
  - Delta: cycles −1.8%, instructions −2.3%
- Throughput (Tiny‑Hot triad, 60k cycles, hakmem only)
  - 32B batch=100: 239.00 → 239.72 M ops/s (+0.3%)
  - 64B batch=100: 241.76 → 244.20 M ops/s (+1.0%)
Notes: PGO+Strict Frontに対して32/64特化は命令数を約2%削減。体感性能は小幅向上。今後は前段の書き込み最小化・補給頻度の最適化を重ねて、さらなるinsns/op低減を狙う。