Files
hakmem/core
Moe Charm (CI) f40be1a5ba Pool TLS: Lock-free MPSC remote queue implementation
Problem: pool_remote_push mutex contention (67% of syscall time in futex)
Solution: Lock-free MPSC queue using atomic CAS operations

Changes:
1. core/pool_tls_remote.c - Lock-free MPSC queue
   - Push: atomic_compare_exchange_weak (CAS loop, no locks!)
   - Pop: atomic_exchange (steal entire chain)
   - Mutex only for RemoteRec creation (rare, first-push-to-thread)

2. core/pool_tls_registry.c - Lock-free lookup
   - Buckets and next pointers now atomic: _Atomic(RegEntry*)
   - Lookup uses memory_order_acquire loads (no locks on hot path)
   - Registration/unregistration still use mutex (rare operations)

Results:
- futex calls: 209 → 7 (-97% reduction!)
- Throughput: 0.97M → 1.0M ops/s (+3%)
- Remaining gap: 5.8x slower than System malloc (5.8M ops/s)

Key Finding:
- futex was NOT the primary bottleneck (only small % of total runtime)
- True bottleneck: 8% cache miss rate + registry lookup overhead

Thread Safety:
- MPSC: Multi-producer (CAS), Single-consumer (owner thread)
- Memory ordering: release/acquire for correctness
- No ABA problem (pointers used once, no reuse)

Next: P0 registry lookup elimination via POOL_TLS_BIND_BOX

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>
2025-11-14 14:29:05 +09:00
..
2025-11-11 21:49:05 +09:00