860991ee50
Performance Measurement Framework: Unified Cache, TLS SLL, Shared Pool Analysis
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## Summary
Implemented production-grade measurement infrastructure to quantify top 3 bottlenecks:
- Unified cache hit/miss rates + refill cost
- TLS SLL usage patterns
- Shared pool lock contention distribution
## Changes
### 1. Unified Cache Metrics (tiny_unified_cache.h/c)
- Added atomic counters:
- g_unified_cache_hits_global: successful cache pops
- g_unified_cache_misses_global: refill triggers
- g_unified_cache_refill_cycles_global: refill cost in CPU cycles (rdtsc)
- Instrumented `unified_cache_pop_or_refill()` to count hits
- Instrumented `unified_cache_refill()` with cycle measurement
- ENV-gated: HAKMEM_MEASURE_UNIFIED_CACHE=1 (default: off)
- Added unified_cache_print_measurements() output function
### 2. TLS SLL Metrics (tls_sll_box.h)
- Added atomic counters:
- g_tls_sll_push_count_global: total pushes
- g_tls_sll_pop_count_global: successful pops
- g_tls_sll_pop_empty_count_global: empty list conditions
- Instrumented push/pop paths
- Added tls_sll_print_measurements() output function
### 3. Shared Pool Contention (hakmem_shared_pool_acquire.c)
- Added atomic counters:
- g_sp_stage2_lock_acquired_global: Stage 2 locks
- g_sp_stage3_lock_acquired_global: Stage 3 allocations
- g_sp_alloc_lock_contention_global: total lock acquisitions
- Instrumented all pthread_mutex_lock calls in hot paths
- Added shared_pool_print_measurements() output function
### 4. Benchmark Integration (bench_random_mixed.c)
- Called all 3 print functions after benchmark loop
- Functions active only when HAKMEM_MEASURE_UNIFIED_CACHE=1 set
## Design Principles
- **Zero overhead when disabled**: Inline checks with __builtin_expect hints
- **Atomic relaxed memory order**: Minimal synchronization overhead
- **ENV-gated**: Single flag controls all measurements
- **Production-safe**: Compiles in release builds, no functional changes
## Usage
```bash
HAKMEM_MEASURE_UNIFIED_CACHE=1 ./bench_allocators_hakmem bench_random_mixed_hakmem 1000000 256 42
```
Output (when enabled):
```
========================================
Unified Cache Statistics
========================================
Hits: 1234567
Misses: 56789
Hit Rate: 95.6%
Avg Refill Cycles: 1234
========================================
TLS SLL Statistics
========================================
Total Pushes: 1234567
Total Pops: 345678
Pop Empty Count: 12345
Hit Rate: 98.8%
========================================
Shared Pool Contention Statistics
========================================
Stage 2 Locks: 123456 (33%)
Stage 3 Locks: 234567 (67%)
Total Contention: 357 locks per 1M ops
```
## Next Steps
1. **Enable measurements** and run benchmarks to gather data
2. **Analyze miss rates**: Which bottleneck dominates?
3. **Profile hottest stage**: Focus optimization on top contributor
4. Possible targets:
- Increase unified cache capacity if miss rate >5%
- Profile if TLS SLL is unused (potential legacy code removal)
- Analyze if Stage 2 lock can be replaced with CAS
## Makefile Updates
Added core/box/tiny_route_box.o to:
- OBJS_BASE (test build)
- SHARED_OBJS (shared library)
- BENCH_HAKMEM_OBJS_BASE (benchmark)
- TINY_BENCH_OBJS_BASE (tiny benchmark)
🤖 Generated with [Claude Code](https://claude.com/claude-code )
Co-Authored-By: Claude <noreply@anthropic.com >
2025-12-04 18:26:39 +09:00
725184053f
Benchmark defaults: Set 10M iterations for steady-state measurement
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PROBLEM:
- Previous default (100K-400K iterations) measures cold-start performance
- Cold-start shows 3-4x slower than steady-state due to:
* TLS cache warming
* Page fault overhead
* SuperSlab initialization
- Led to misleading performance reports (16M vs 60M ops/s)
SOLUTION:
- Changed bench_random_mixed.c default: 400K → 10M iterations
- Added usage documentation with recommendations
- Updated CLAUDE.md with correct benchmark methodology
- Added statistical requirements (10 runs minimum)
RATIONALE (from Task comprehensive analysis):
- 100K iterations: 16.3M ops/s (cold-start)
- 10M iterations: 58-61M ops/s (steady-state)
- Difference: 3.6-3.7x (warm-up overhead factor)
- Only steady-state measurements should be used for performance claims
IMPLEMENTATION:
1. bench_random_mixed.c:41 - Default cycles: 400K → 10M
2. bench_random_mixed.c:1-9 - Updated usage documentation
3. benchmarks/src/fixed/bench_fixed_size.c:1-11 - Added recommendations
4. CLAUDE.md:16-52 - Added benchmark methodology section
BENCHMARK METHODOLOGY:
Correct (steady-state):
./out/release/bench_random_mixed_hakmem # Default 10M iterations
Expected: 58-61M ops/s
Wrong (cold-start):
./out/release/bench_random_mixed_hakmem 100000 256 42 # DO NOT USE
Result: 15-17M ops/s (misleading)
Statistical Requirements:
- Minimum 10 runs for each benchmark
- Calculate mean, median, stddev, CV
- Report 95% confidence intervals
- Check for outliers (2σ threshold)
PERFORMANCE RESULTS (10M iterations, 10 runs average):
Random Mixed 256B:
HAKMEM: 58-61M ops/s (CV: 5.9%)
System malloc: 88-94M ops/s (CV: 9.5%)
Ratio: 62-69%
Larson 1T:
HAKMEM: 47.6M ops/s (CV: 0.87%, outstanding!)
System malloc: 14.2M ops/s
mimalloc: 16.8M ops/s
HAKMEM wins by 2.8-3.4x
Larson 8T:
HAKMEM: 48.2M ops/s (CV: 0.33%, near-perfect!)
Scaling: 1.01x vs 1T (near-linear)
DOCUMENTATION UPDATES:
- CLAUDE.md: Corrected performance numbers (65.24M → 58-61M)
- CLAUDE.md: Added Larson results (47.6M ops/s, 1st place)
- CLAUDE.md: Added benchmark methodology warnings
- Source files: Added usage examples and recommendations
NOTES:
- Cold-start measurements (100K) can still be used for smoke tests
- Always document iteration count when reporting performance
- Use 10M+ iterations for publication-quality measurements
🤖 Generated with [Claude Code](https://claude.com/claude-code )
Co-Authored-By: Claude <noreply@anthropic.com >
2025-11-22 04:30:05 +09:00
