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Mid-Large Phase 12 Complete + P0-5 Lock-Free Stage 2

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**Phase 12 第1ラウンド完了** ✅
- 0.24M → 2.39M ops/s (8T, **+896%**)
- SEGFAULT → Zero crashes (**100% → 0%**)
- futex: 209 → 10 calls (**-95%**)

**P0-5: Lock-Free Stage 2 (Slot Claiming)**
- Atomic SlotState: `_Atomic SlotState state`
- sp_slot_claim_lockfree(): CAS-based UNUSED→ACTIVE transition
- acquire_slab() Stage 2: Lock-free claiming (mutex only for metadata)
- Result: 2.34M → 2.39M ops/s (+2.5% @ 8T)

**Implementation**:
- core/hakmem_shared_pool.h: Atomic SlotState definition
- core/hakmem_shared_pool.c:
  - sp_slot_claim_lockfree() (+40 lines)
  - Atomic helpers: sp_slot_find_unused/mark_active/mark_empty
  - Stage 2 lock-free integration
- Verified via debug logs: STAGE2_LOCKFREE claiming works

**Reports**:
- MID_LARGE_P0_PHASE_REPORT.md: P0-0 to P0-4 comprehensive summary
- MID_LARGE_FINAL_AB_REPORT.md: Complete Phase 12 A/B comparison (17KB)
  - Performance evolution table
  - Lock contention analysis  - Lessons learned
  - File inventory

**Tiny Baseline Measurement** 📊
- System malloc: 82.9M ops/s (256B)
- HAKMEM:        8.88M ops/s (256B)
- **Gap: 9.3x slower** (target for next phase)

**Next**: Tiny allocator optimization (drain interval, front cache, perf profile)

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

Co-Authored-By: Claude <noreply@anthropic.com>
This commit is contained in:
Moe Charm (CI)
2025-11-14 16:51:53 +09:00
parent 29fefa2018
commit ec453d67f2
4 changed files with 1489 additions and 62 deletions
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308
core/hakmem_shared_pool.c
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@ -48,6 +48,34 @@ static void __attribute__((destructor)) lock_stats_report(void) {
fprintf(stderr, "===================================\n");
}
// ============================================================================
// P0-4: Lock-Free Free Slot List - Node Pool
// ============================================================================
// Pre-allocated node pools (one per class, to avoid malloc/free)
FreeSlotNode g_free_node_pool[TINY_NUM_CLASSES_SS][MAX_FREE_NODES_PER_CLASS];
_Atomic uint32_t g_node_alloc_index[TINY_NUM_CLASSES_SS] = {0};
// Allocate a node from pool (lock-free, never fails until pool exhausted)
static inline FreeSlotNode* node_alloc(int class_idx) {
if (class_idx < 0 || class_idx >= TINY_NUM_CLASSES_SS) {
return NULL;
}
uint32_t idx = atomic_fetch_add(&g_node_alloc_index[class_idx], 1);
if (idx >= MAX_FREE_NODES_PER_CLASS) {
// Pool exhausted - should not happen in practice
static _Atomic int warn_once = 0;
if (atomic_exchange(&warn_once, 1) == 0) {
fprintf(stderr, "[P0-4 WARN] Node pool exhausted for class %d\n", class_idx);
}
return NULL;
}
return &g_free_node_pool[class_idx][idx];
}
// ============================================================================
// Phase 12-2: SharedSuperSlabPool skeleton implementation
// Goal:
// - Centralize SuperSlab allocation/registration
@ -69,8 +97,11 @@ SharedSuperSlabPool g_shared_pool = {
.lru_head = NULL,
.lru_tail = NULL,
.lru_count = 0,
// P0-4: Lock-free free slot lists (zero-initialized atomic pointers)
.free_slots_lockfree = {{.head = ATOMIC_VAR_INIT(NULL)}},
// Legacy: mutex-protected free lists
.free_slots = {{.entries = {{0}}, .count = 0}},
// Phase 12: SP-SLOT fields
.free_slots = {{.entries = {{0}}, .count = 0}}, // Zero-init all class free lists
.ss_metadata = NULL,
.ss_meta_capacity = 0,
.ss_meta_count = 0
@ -122,12 +153,14 @@ shared_pool_init(void)
// ---------- Layer 1: Slot Operations (Low-level) ----------
// Find first unused slot in SharedSSMeta
// P0-5: Uses atomic load for state check
// Returns: slot_idx on success, -1 if no unused slots
static int sp_slot_find_unused(SharedSSMeta* meta) {
if (!meta) return -1;
for (int i = 0; i < meta->total_slots; i++) {
if (meta->slots[i].state == SLOT_UNUSED) {
SlotState state = atomic_load_explicit(&meta->slots[i].state, memory_order_acquire);
if (state == SLOT_UNUSED) {
return i;
}
}
@ -135,6 +168,7 @@ static int sp_slot_find_unused(SharedSSMeta* meta) {
}
// Mark slot as ACTIVE (UNUSED→ACTIVE or EMPTY→ACTIVE)
// P0-5: Uses atomic store for state transition (caller must hold mutex!)
// Returns: 0 on success, -1 on error
static int sp_slot_mark_active(SharedSSMeta* meta, int slot_idx, int class_idx) {
if (!meta || slot_idx < 0 || slot_idx >= meta->total_slots) return -1;
@ -142,9 +176,12 @@ static int sp_slot_mark_active(SharedSSMeta* meta, int slot_idx, int class_idx)
SharedSlot* slot = &meta->slots[slot_idx];
// Load state atomically
SlotState state = atomic_load_explicit(&slot->state, memory_order_acquire);
// Transition: UNUSED→ACTIVE or EMPTY→ACTIVE
if (slot->state == SLOT_UNUSED || slot->state == SLOT_EMPTY) {
slot->state = SLOT_ACTIVE;
if (state == SLOT_UNUSED || state == SLOT_EMPTY) {
atomic_store_explicit(&slot->state, SLOT_ACTIVE, memory_order_release);
slot->class_idx = (uint8_t)class_idx;
slot->slab_idx = (uint8_t)slot_idx;
meta->active_slots++;
@ -155,14 +192,18 @@ static int sp_slot_mark_active(SharedSSMeta* meta, int slot_idx, int class_idx)
}
// Mark slot as EMPTY (ACTIVE→EMPTY)
// P0-5: Uses atomic store for state transition (caller must hold mutex!)
// Returns: 0 on success, -1 on error
static int sp_slot_mark_empty(SharedSSMeta* meta, int slot_idx) {
if (!meta || slot_idx < 0 || slot_idx >= meta->total_slots) return -1;
SharedSlot* slot = &meta->slots[slot_idx];
if (slot->state == SLOT_ACTIVE) {
slot->state = SLOT_EMPTY;
// Load state atomically
SlotState state = atomic_load_explicit(&slot->state, memory_order_acquire);
if (state == SLOT_ACTIVE) {
atomic_store_explicit(&slot->state, SLOT_EMPTY, memory_order_release);
if (meta->active_slots > 0) {
meta->active_slots--;
}
@ -228,8 +269,9 @@ static SharedSSMeta* sp_meta_find_or_create(SuperSlab* ss) {
meta->active_slots = 0;
// Initialize all slots as UNUSED
// P0-5: Use atomic store for state initialization
for (int i = 0; i < meta->total_slots; i++) {
meta->slots[i].state = SLOT_UNUSED;
atomic_store_explicit(&meta->slots[i].state, SLOT_UNUSED, memory_order_relaxed);
meta->slots[i].class_idx = 0;
meta->slots[i].slab_idx = (uint8_t)i;
}
@ -279,6 +321,118 @@ static int sp_freelist_pop(int class_idx, SharedSSMeta** out_meta, int* out_slot
return 1;
}
// ============================================================================
// P0-5: Lock-Free Slot Claiming (Stage 2 Optimization)
// ============================================================================
// Try to claim an UNUSED slot via lock-free CAS
// Returns: slot_idx on success, -1 if no UNUSED slots available
// LOCK-FREE: Can be called from any thread without mutex
static int sp_slot_claim_lockfree(SharedSSMeta* meta, int class_idx) {
if (!meta) return -1;
if (class_idx < 0 || class_idx >= TINY_NUM_CLASSES_SS) return -1;
// Scan all slots for UNUSED state
for (int i = 0; i < meta->total_slots; i++) {
SlotState expected = SLOT_UNUSED;
// Try to claim this slot atomically (UNUSED → ACTIVE)
if (atomic_compare_exchange_strong_explicit(
&meta->slots[i].state,
&expected,
SLOT_ACTIVE,
memory_order_acq_rel, // Success: acquire+release semantics
memory_order_relaxed // Failure: just retry next slot
)) {
// Successfully claimed! Update non-atomic fields
// (Safe because we now own this slot)
meta->slots[i].class_idx = (uint8_t)class_idx;
meta->slots[i].slab_idx = (uint8_t)i;
// Increment active_slots counter atomically
// (Multiple threads may claim slots concurrently)
atomic_fetch_add_explicit(
(_Atomic uint8_t*)&meta->active_slots, 1,
memory_order_relaxed
);
return i; // Return claimed slot index
}
// CAS failed (slot was not UNUSED) - continue to next slot
}
return -1; // No UNUSED slots available
}
// ============================================================================
// P0-4: Lock-Free Free Slot List Operations
// ============================================================================
// Push empty slot to lock-free per-class free list (LIFO)
// LOCK-FREE: Can be called from any thread without mutex
// Returns: 0 on success, -1 on failure (node pool exhausted)
static int sp_freelist_push_lockfree(int class_idx, SharedSSMeta* meta, int slot_idx) {
if (class_idx < 0 || class_idx >= TINY_NUM_CLASSES_SS) return -1;
if (!meta || slot_idx < 0 || slot_idx >= meta->total_slots) return -1;
// Allocate node from pool
FreeSlotNode* node = node_alloc(class_idx);
if (!node) {
return -1; // Pool exhausted
}
// Fill node data
node->meta = meta;
node->slot_idx = (uint8_t)slot_idx;
// Lock-free LIFO push using CAS loop
LockFreeFreeList* list = &g_shared_pool.free_slots_lockfree[class_idx];
FreeSlotNode* old_head = atomic_load_explicit(&list->head, memory_order_relaxed);
do {
node->next = old_head;
} while (!atomic_compare_exchange_weak_explicit(
&list->head, &old_head, node,
memory_order_release, // Success: publish node to other threads
memory_order_relaxed // Failure: retry with updated old_head
));
return 0; // Success
}
// Pop empty slot from lock-free per-class free list (LIFO)
// LOCK-FREE: Can be called from any thread without mutex
// Returns: 1 if popped (out params filled), 0 if list empty
static int sp_freelist_pop_lockfree(int class_idx, SharedSSMeta** out_meta, int* out_slot_idx) {
if (class_idx < 0 || class_idx >= TINY_NUM_CLASSES_SS) return 0;
if (!out_meta || !out_slot_idx) return 0;
LockFreeFreeList* list = &g_shared_pool.free_slots_lockfree[class_idx];
FreeSlotNode* old_head = atomic_load_explicit(&list->head, memory_order_acquire);
// Lock-free LIFO pop using CAS loop
do {
if (old_head == NULL) {
return 0; // List empty
}
} while (!atomic_compare_exchange_weak_explicit(
&list->head, &old_head, old_head->next,
memory_order_acquire, // Success: acquire node data
memory_order_acquire // Failure: retry with updated old_head
));
// Extract data from popped node
*out_meta = old_head->meta;
*out_slot_idx = old_head->slot_idx;
// NOTE: We do NOT free the node back to pool (no node recycling yet)
// This is acceptable because MAX_FREE_NODES_PER_CLASS (512) is generous
// and workloads typically don't push/pop the same slot repeatedly
return 1; // Success
}
/*
* Internal: allocate and register a new SuperSlab for the shared pool.
*
@ -383,27 +537,31 @@ shared_pool_acquire_slab(int class_idx, SuperSlab** ss_out, int* slab_idx_out)
dbg_acquire = (e && *e && *e != '0') ? 1 : 0;
}
// P0 instrumentation: count lock acquisitions
lock_stats_init();
if (g_lock_stats_enabled == 1) {
atomic_fetch_add(&g_lock_acquire_count, 1);
atomic_fetch_add(&g_lock_acquire_slab_count, 1);
}
pthread_mutex_lock(&g_shared_pool.alloc_lock);
// ========== Stage 1: Reuse EMPTY slots from free list ==========
// ========== Stage 1 (Lock-Free): Try to reuse EMPTY slots ==========
// P0-4: Lock-free pop from per-class free list (no mutex needed!)
// Best case: Same class freed a slot, reuse immediately (cache-hot)
SharedSSMeta* reuse_meta = NULL;
int reuse_slot_idx = -1;
if (sp_freelist_pop(class_idx, &reuse_meta, &reuse_slot_idx)) {
// Found EMPTY slot for this class - reactivate it
if (sp_freelist_pop_lockfree(class_idx, &reuse_meta, &reuse_slot_idx)) {
// Found EMPTY slot from lock-free list!
// Now acquire mutex ONLY for slot activation and metadata update
// P0 instrumentation: count lock acquisitions
lock_stats_init();
if (g_lock_stats_enabled == 1) {
atomic_fetch_add(&g_lock_acquire_count, 1);
atomic_fetch_add(&g_lock_acquire_slab_count, 1);
}
pthread_mutex_lock(&g_shared_pool.alloc_lock);
// Activate slot under mutex (slot state transition requires protection)
if (sp_slot_mark_active(reuse_meta, reuse_slot_idx, class_idx) == 0) {
SuperSlab* ss = reuse_meta->ss;
if (dbg_acquire == 1) {
fprintf(stderr, "[SP_ACQUIRE_STAGE1] class=%d reusing EMPTY slot (ss=%p slab=%d)\n",
fprintf(stderr, "[SP_ACQUIRE_STAGE1_LOCKFREE] class=%d reusing EMPTY slot (ss=%p slab=%d)\n",
class_idx, (void*)ss, reuse_slot_idx);
}
@ -427,50 +585,83 @@ shared_pool_acquire_slab(int class_idx, SuperSlab** ss_out, int* slab_idx_out)
atomic_fetch_add(&g_lock_release_count, 1);
}
pthread_mutex_unlock(&g_shared_pool.alloc_lock);
return 0; // ✅ Stage 1 success
return 0; // ✅ Stage 1 (lock-free) success
}
// Slot activation failed (race condition?) - release lock and fall through
if (g_lock_stats_enabled == 1) {
atomic_fetch_add(&g_lock_release_count, 1);
}
pthread_mutex_unlock(&g_shared_pool.alloc_lock);
}
// ========== Stage 2: Find UNUSED slots in existing SuperSlabs ==========
// Scan all SuperSlabs for UNUSED slots
for (uint32_t i = 0; i < g_shared_pool.ss_meta_count; i++) {
// ========== Stage 2 (Lock-Free): Try to claim UNUSED slots ==========
// P0-5: Lock-free atomic CAS claiming (no mutex needed for slot state transition!)
// Read ss_meta_count atomically (safe: only grows, never shrinks)
uint32_t meta_count = atomic_load_explicit(
(_Atomic uint32_t*)&g_shared_pool.ss_meta_count,
memory_order_acquire
);
for (uint32_t i = 0; i < meta_count; i++) {
SharedSSMeta* meta = &g_shared_pool.ss_metadata[i];
int unused_idx = sp_slot_find_unused(meta);
if (unused_idx >= 0) {
// Found UNUSED slot - activate it
if (sp_slot_mark_active(meta, unused_idx, class_idx) == 0) {
SuperSlab* ss = meta->ss;
// Try lock-free claiming (UNUSED → ACTIVE via CAS)
int claimed_idx = sp_slot_claim_lockfree(meta, class_idx);
if (claimed_idx >= 0) {
// Successfully claimed slot! Now acquire mutex ONLY for metadata update
SuperSlab* ss = meta->ss;
if (dbg_acquire == 1) {
fprintf(stderr, "[SP_ACQUIRE_STAGE2] class=%d using UNUSED slot (ss=%p slab=%d)\n",
class_idx, (void*)ss, unused_idx);
}
// Update SuperSlab metadata
ss->slab_bitmap |= (1u << unused_idx);
ss->slabs[unused_idx].class_idx = (uint8_t)class_idx;
if (ss->active_slabs == 0) {
ss->active_slabs = 1;
g_shared_pool.active_count++;
}
// Update hint
g_shared_pool.class_hints[class_idx] = ss;
*ss_out = ss;
*slab_idx_out = unused_idx;
if (g_lock_stats_enabled == 1) {
atomic_fetch_add(&g_lock_release_count, 1);
}
pthread_mutex_unlock(&g_shared_pool.alloc_lock);
return 0; // ✅ Stage 2 success
if (dbg_acquire == 1) {
fprintf(stderr, "[SP_ACQUIRE_STAGE2_LOCKFREE] class=%d claimed UNUSED slot (ss=%p slab=%d)\n",
class_idx, (void*)ss, claimed_idx);
}
// P0 instrumentation: count lock acquisitions
lock_stats_init();
if (g_lock_stats_enabled == 1) {
atomic_fetch_add(&g_lock_acquire_count, 1);
atomic_fetch_add(&g_lock_acquire_slab_count, 1);
}
pthread_mutex_lock(&g_shared_pool.alloc_lock);
// Update SuperSlab metadata under mutex
ss->slab_bitmap |= (1u << claimed_idx);
ss->slabs[claimed_idx].class_idx = (uint8_t)class_idx;
if (ss->active_slabs == 0) {
ss->active_slabs = 1;
g_shared_pool.active_count++;
}
// Update hint
g_shared_pool.class_hints[class_idx] = ss;
*ss_out = ss;
*slab_idx_out = claimed_idx;
if (g_lock_stats_enabled == 1) {
atomic_fetch_add(&g_lock_release_count, 1);
}
pthread_mutex_unlock(&g_shared_pool.alloc_lock);
return 0; // ✅ Stage 2 (lock-free) success
}
// Claim failed (no UNUSED slots in this meta) - continue to next SuperSlab
}
// ========== Stage 3: Mutex-protected fallback (new SuperSlab allocation) ==========
// All existing SuperSlabs have no UNUSED slots → need new SuperSlab
// P0 instrumentation: count lock acquisitions
lock_stats_init();
if (g_lock_stats_enabled == 1) {
atomic_fetch_add(&g_lock_acquire_count, 1);
atomic_fetch_add(&g_lock_acquire_slab_count, 1);
}
pthread_mutex_lock(&g_shared_pool.alloc_lock);
// ========== Stage 3: Get new SuperSlab ==========
// Try LRU cache first, then mmap
SuperSlab* new_ss = NULL;
@ -631,13 +822,14 @@ shared_pool_release_slab(SuperSlab* ss, int slab_idx)
}
}
// Push to per-class free list (enables reuse by same class)
// P0-4: Push to lock-free per-class free list (enables reuse by same class)
// Note: push BEFORE releasing mutex (slot state already updated under lock)
if (class_idx < TINY_NUM_CLASSES_SS) {
sp_freelist_push(class_idx, sp_meta, slab_idx);
sp_freelist_push_lockfree(class_idx, sp_meta, slab_idx);
if (dbg == 1) {
fprintf(stderr, "[SP_SLOT_FREELIST] class=%d pushed slot (ss=%p slab=%d) count=%u active_slots=%u/%u\n",
class_idx, (void*)ss, slab_idx, g_shared_pool.free_slots[class_idx].count,
fprintf(stderr, "[SP_SLOT_FREELIST_LOCKFREE] class=%d pushed slot (ss=%p slab=%d) active_slots=%u/%u\n",
class_idx, (void*)ss, slab_idx,
sp_meta->active_slots, sp_meta->total_slots);
}
}