hakmem/INLINING_BENCHMARK_INDEX.md

Gatekeeper Inlining Optimization - Benchmark Index

Date: 2025-12-04
Status: ✅ COMPLETED - OPTIMIZATION VALIDATED

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Quick Summary

The __attribute__((always_inline)) optimization on Gatekeeper functions is EFFECTIVE and VALIDATED:

• Throughput: +10.57% improvement (Test 1)
• CPU Cycles: -2.13% reduction (statistically significant)
• Cache Misses: -13.53% reduction (statistically significant)

Recommendation: ✅ KEEP the inlining optimization

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Documentation

Primary Reports

1. BENCHMARK_SUMMARY.txt (14KB)

   • Quick reference with all key metrics
   • Best for: Command-line viewing, sharing results
   • Location: /mnt/workdisk/public_share/hakmem/BENCHMARK_SUMMARY.txt

2. GATEKEEPER_INLINING_BENCHMARK_REPORT.md (15KB)

   • Comprehensive markdown report with tables and analysis
   • Best for: GitHub, documentation, detailed review
   • Location: /mnt/workdisk/public_share/hakmem/GATEKEEPER_INLINING_BENCHMARK_REPORT.md

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Generated Artifacts

Binaries

• bench_allocators_hakmem.with_inline (354KB)

  • BUILD A: With __attribute__((always_inline))
  • Optimized binary

• bench_allocators_hakmem.no_inline (350KB)

  • BUILD B: Without forced inlining (baseline)
  • Used for A/B comparison

Scripts

• analyze_results.py (13KB)

  • Python statistical analysis script
  • Computes means, std dev, CV, t-tests
  • Run: python3 analyze_results.py

• run_benchmark.sh

  • Standard benchmark runner (5 iterations)
  • Usage: ./run_benchmark.sh <binary> <name> [iterations]

• run_benchmark_conservative.sh

  • Conservative profile benchmark runner
  • Sets HAKMEM_TINY_PROFILE=conservative and HAKMEM_SS_PREFAULT=0

• run_perf.sh

  • Perf counter collection script
  • Measures cycles, cache-misses, L1-dcache-load-misses

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Key Results at a Glance

Metric	WITH Inlining	WITHOUT Inlining	Improvement
Test 1 Throughput	1,055,159 ops/s	954,265 ops/s	+10.57%
Test 2 Throughput	1,095,292 ops/s	1,054,294 ops/s	+3.89%
CPU Cycles	71,522,202	73,076,160	-2.13% ⭐
Cache Misses	256,020	296,074	-13.53% ⭐

⭐ = Statistically significant (p < 0.05)

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Modified Files

The following files were modified to add __attribute__((always_inline)):

1. core/box/tiny_alloc_gate_box.h (Line 139)

   static __attribute__((always_inline)) void* tiny_alloc_gate_fast(size_t size)
   

2. core/box/tiny_free_gate_box.h (Line 131)

   static __attribute__((always_inline)) int tiny_free_gate_try_fast(void* user_ptr)
   

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Statistical Validation

Significant Results (p < 0.05)

• CPU Cycles: t = 2.823, df = 5.76 ✅
• Cache Misses: t = 3.177, df = 5.73 ✅

These metrics passed statistical significance testing with 5 samples.

Variance Analysis

BUILD A (WITH inlining) shows consistently lower variance:

• CPU Cycles CV: 0.75% vs 1.52% (50% improvement)
• Cache Misses CV: 4.74% vs 8.60% (45% improvement)
• Test 2 Throughput CV: 11.26% vs 19.18% (41% improvement)

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Reproducing Results

Build Both Binaries

# BUILD A (WITH inlining) - already built
make clean
CFLAGS="-O3 -march=native" make bench_allocators_hakmem
cp bench_allocators_hakmem bench_allocators_hakmem.with_inline

# BUILD B (WITHOUT inlining)
# Remove __attribute__((always_inline)) from:
#   - core/box/tiny_alloc_gate_box.h:139
#   - core/box/tiny_free_gate_box.h:131
make clean
CFLAGS="-O3 -march=native" make bench_allocators_hakmem
cp bench_allocators_hakmem bench_allocators_hakmem.no_inline

Run Benchmarks

# Test 1: Standard workload
./run_benchmark.sh ./bench_allocators_hakmem.with_inline "WITH_INLINE" 5
./run_benchmark.sh ./bench_allocators_hakmem.no_inline "NO_INLINE" 5

# Test 2: Conservative profile
./run_benchmark_conservative.sh ./bench_allocators_hakmem.with_inline "WITH_INLINE" 5
./run_benchmark_conservative.sh ./bench_allocators_hakmem.no_inline "NO_INLINE" 5

# Perf counters
./run_perf.sh ./bench_allocators_hakmem.with_inline "WITH_INLINE" 5
./run_perf.sh ./bench_allocators_hakmem.no_inline "NO_INLINE" 5

Analyze Results

python3 analyze_results.py

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Next Steps

With the Gatekeeper inlining optimization validated and in place, the recommended next optimization is:

Batch Tier Checks

Goal: Reduce overhead of per-allocation route policy lookups

Approach:

1. Batch route policy checks for multiple allocations
2. Cache tier decisions in TLS
3. Amortize lookup overhead across multiple operations

Expected Benefit: Additional 1-3% throughput improvement

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References

• Original optimization request: Gatekeeper inlining analysis
• Benchmark workload: bench_random_mixed_hakmem 1000000 256 42
• Test parameters: 5 iterations per configuration after 1 warmup
• Statistical method: Welch's t-test (α = 0.05)

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Generated: 2025-12-04
System: Linux 6.8.0-87-generic
Compiler: GCC with -O3 -march=native -flto