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984cca41eff08d4a385a7f57c67605c482560536
hakmem/core/hakmem_tiny_stats_api.h
Moe Charm (CI) 984cca41ef P0 Optimization: Shared Pool fast path with O(1) metadata lookup 
Performance Results:
- Throughput: 2.66M ops/s → 3.8M ops/s (+43% improvement)
- sp_meta_find_or_create: O(N) linear scan → O(1) direct pointer
- Stage 2 metadata scan: 100% → 10-20% (80-90% reduction via hints)

Core Optimizations:

1. O(1) Metadata Lookup (superslab_types.h)
   - Added `shared_meta` pointer field to SuperSlab struct
   - Eliminates O(N) linear search through ss_metadata[] array
   - First access: O(N) scan + cache | Subsequent: O(1) direct return

2. sp_meta_find_or_create Fast Path (hakmem_shared_pool.c)
   - Check cached ss->shared_meta first before linear scan
   - Cache pointer after successful linear scan for future lookups
   - Reduces 7.8% CPU hotspot to near-zero for hot paths

3. Stage 2 Class Hints Fast Path (hakmem_shared_pool_acquire.c)
   - Try class_hints[class_idx] FIRST before full metadata scan
   - Uses O(1) ss->shared_meta lookup for hint validation
   - __builtin_expect() for branch prediction optimization
   - 80-90% of acquire calls now skip full metadata scan

4. Proper Initialization (ss_allocation_box.c)
   - Initialize shared_meta = NULL in superslab_allocate()
   - Ensures correct NULL-check semantics for new SuperSlabs

Additional Improvements:
- Updated ptr_trace and debug ring for release build efficiency
- Enhanced ENV variable documentation and analysis
- Added learner_env_box.h for configuration management
- Various Box optimizations for reduced overhead

Thread Safety:
- All atomic operations use correct memory ordering
- shared_meta cached under mutex protection
- Lock-free Stage 2 uses proper CAS with acquire/release semantics

Testing:
- Benchmark: 1M iterations, 3.8M ops/s stable
- Build: Clean compile RELEASE=0 and RELEASE=1
- No crashes, memory leaks, or correctness issues

Next Optimization Candidates:
- P1: Per-SuperSlab free slot bitmap for O(1) slot claiming
- P2: Reduce Stage 2 critical section size
- P3: Page pre-faulting (MAP_POPULATE)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
2025-12-04 16:21:54 +09:00

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#ifndef HAKMEM_TINY_STATS_API_H
#define HAKMEM_TINY_STATS_API_H
#include <stdint.h>
#include <stddef.h>
#include <stdatomic.h>
// Phase 2, Module 1: Statistics and Debug API
// Extracted from hakmem_tiny.c (lines 4348-4728)
// Cold path functions - zero performance impact
// Statistics API
void hak_tiny_get_stats(uint64_t* alloc_count, uint64_t* free_count, uint64_t* slab_count);
void hak_tiny_print_stats(void);
// Memory profiling (toggle with HAKMEM_DEBUG_MEMORY)
void hak_tiny_print_memory_profile(void);
// Debug counters (toggle with HAKMEM_DEBUG_COUNTERS)
void hak_tiny_ultra_debug_dump(void);
void hak_tiny_path_debug_dump(void);
void hak_tiny_debug_counters_dump(void);
// Immediate dump of all counters (Refill/Publish/Free/Cache)
void hak_tiny_dump_all_counters_now(void);
// Cooperative stats polling hook (no-op since Phase 4d master stats)
static inline __attribute__((always_inline)) void hak_tiny_stats_poll(void) {
(void)0;
}
// SuperSlab adopt/publish debug counters (per class)
extern unsigned long long g_ss_publish_dbg[];
extern unsigned long long g_ss_adopt_dbg[];
// Slab-ring counters (per class)
extern unsigned long long g_slab_publish_dbg[];
extern unsigned long long g_slab_adopt_dbg[];
extern unsigned long long g_slab_requeue_dbg[];
extern unsigned long long g_slab_miss_dbg[];
// Refill-stage counters
extern unsigned long long g_rf_total_calls[];
extern unsigned long long g_rf_hit_bench[];
extern unsigned long long g_rf_hit_hot[];
extern unsigned long long g_rf_hit_mail[];
extern unsigned long long g_rf_hit_slab[];
extern unsigned long long g_rf_hit_ss[];
extern unsigned long long g_rf_hit_reg[];
extern unsigned long long g_rf_mmap_calls[];
extern unsigned long long g_rf_time_total_ns[];
extern unsigned long long g_rf_time_hot_ns[];
extern unsigned long long g_rf_time_bench_ns[];
extern unsigned long long g_rf_time_mail_ns[];
extern unsigned long long g_rf_time_slab_ns[];
extern unsigned long long g_rf_time_ss_ns[];
extern unsigned long long g_rf_time_reg_ns[];
extern unsigned long long g_rf_time_mmap_ns[];
extern unsigned long long g_pub_mail_hits[];
extern unsigned long long g_pub_hot_hits[];
extern unsigned long long g_pub_bench_hits[];
// Free pipeline visibility
extern unsigned long long g_free_via_ss_local[];
extern unsigned long long g_free_via_ss_remote[];
extern unsigned long long g_free_via_tls_sll[];
extern unsigned long long g_free_via_mag[];
// Front Gate Breakdown (debug counters)
extern unsigned long long g_front_sfc_hit[];
extern unsigned long long g_front_sll_hit[];
extern unsigned long long g_front_quick_hit[];
extern unsigned long long g_front_mag_hit[];
// Free-side trigger counters
extern unsigned long long g_first_free_transitions[];
extern unsigned long long g_remote_free_transitions[];
// Adopt/Registry gate counters
extern unsigned long long g_adopt_gate_calls[];
extern unsigned long long g_adopt_gate_success[];
extern unsigned long long g_reg_scan_attempts[];
extern unsigned long long g_reg_scan_hits[];
extern unsigned long long g_free_via_fast_tls[];
extern unsigned long long g_free_via_fastcache[];
extern unsigned long long g_fast_spare_flush[];
extern unsigned long long g_fast_push_hits[];
extern unsigned long long g_fast_push_full[];
extern unsigned long long g_fast_push_disabled[];
extern unsigned long long g_fast_push_zero_cap[];
extern unsigned long long g_fast_push_gate_disabled[];
extern unsigned long long g_fast_push_gate_zero_cap[];
extern unsigned long long g_fast_spare_attempts[];
extern unsigned long long g_fast_spare_disabled[];
extern unsigned long long g_fast_spare_empty[];
extern unsigned long long g_fast_spare_lookup_fail[];
extern unsigned long long g_fast_spare_bad_index[];
extern unsigned long long g_fast_lookup_ss[];
extern unsigned long long g_fast_lookup_slab[];
extern unsigned long long g_fast_lookup_none;
// Publish pipeline visibility
extern unsigned long long g_pub_notify_calls[];
extern unsigned long long g_pub_same_empty[];
extern unsigned long long g_remote_transitions[];
extern unsigned long long g_mailbox_register_calls[];
extern unsigned long long g_mailbox_slow_discoveries[];
extern uint64_t g_ss_cache_hits[];
extern uint64_t g_ss_cache_misses[];
extern uint64_t g_ss_cache_puts[];
extern uint64_t g_ss_cache_drops[];
extern uint64_t g_ss_cache_precharged[];
extern uint64_t g_superslabs_reused;
extern uint64_t g_superslabs_cached;
#endif // HAKMEM_TINY_STATS_API_H
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