Module memory_stats 

Cross-thread memory statistics registry

Provides visibility into arena and pool memory usage across all worker threads. Each thread registers itself and updates its own slot with minimal overhead.

Design

The challenge: Arena and pool are thread-local, but diagnostics runs on a separate signal handler thread. We solve this with a global registry where each thread has an exclusive slot for its stats.

┌─────────────────────────────────────────────────────────┐
│              MemoryStatsRegistry (global)               │
├─────────────────────────────────────────────────────────┤
│ slots: [MemorySlot; MAX_THREADS]                        │
│                                                         │
│  ┌──────────────────┐  ┌──────────────────┐             │
│  │ Slot 0 (Thread A)│  │ Slot 1 (Thread B)│  ...        │
│  │ thread_id: u64   │  │ thread_id: u64   │             │
│  │ arena_bytes: u64 │  │ arena_bytes: u64 │             │
│  │ pool_free: u64   │  │ pool_free: u64   │             │
│  │ pool_allocs: u64 │  │ pool_allocs: u64 │             │
│  └──────────────────┘  └──────────────────┘             │
└─────────────────────────────────────────────────────────┘

Performance

• Registration: One-time CAS per thread (on first arena access)
• Updates: Single atomic store per operation (~1-2 cycles, no contention)
• Reads: Only during diagnostics (SIGQUIT), iterates all slots

This maintains the “fast path stays fast” principle.

Structs

AggregateMemoryStats

Aggregated memory statistics across all threads

MemorySlot

Statistics for a single thread’s memory usage

MemoryStatsRegistry

Global registry for cross-thread memory statistics

ThreadMemoryStats

Memory statistics for a single thread

Functions

get_or_register_slot

Get or register the current thread’s slot index

increment_pool_allocations

Increment pool allocation counter for the current thread

memory_registry

Get the global memory stats registry

update_arena_stats

Update arena stats for the current thread

update_pool_stats

Update pool stats for the current thread