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perf: 多 shard 锁数组按 64B 对齐，修复 >8 线程吞吐断崖（10–20 线程 1.6–3.7×） #15

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Merged
carsontung666 merged 1 commit into from
Oct 31, 2026
Merged

perf: 多 shard 锁数组按 64B 对齐，修复 >8 线程吞吐断崖（10–20 线程 1.6–3.7×） #15

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29 changes: 22 additions & 7 deletions include/slotsboxmalloc/slotsboxobj.h
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Original file line number Diff line number Diff line change
Expand Up @@ -123,9 +123,16 @@ typedef struct {
uint8_t slot_shift;
uint8_t box_off;
uint32_t max_blocks;
uint8_t _pad[2];
uint8_t layout; /* SBO_LAYOUT_LOCK64 when root_slots > 1, else 0 */
uint8_t _pad[1];
} sbo_meta_t;

/* Multi-shard metas place the lock array on a 64-byte boundary relative to
* meta (pass a 64-byte aligned meta, e.g. from mmap) so each shard's lock and
* hot cache own one cache line. Multi-shard metas from v0.1.7 (layout 0) are
* rejected rather than misread; the single-shard layout is unchanged. */
#define SBO_LAYOUT_LOCK64 1

int sbo_init(void *metaptr, size_t head_size, size_t data_size);
uint64_t sbo_alloc(void *metaptr, size_t size);
void sbo_free(void *metaptr, uint64_t obj_offset);
Expand All @@ -144,12 +151,18 @@ size_t sbo_meta_size(size_t data_size, size_t per_slot_pool);
static inline blocks_meta_t *sbo_pool_meta(sbo_meta_t *meta, uint8_t si) {
return (blocks_meta_t *)((uint8_t *)(meta + 1)) + si;
}
static inline size_t sbo_lock_off(uint8_t shards) {
size_t off = sizeof(sbo_meta_t) + (size_t)shards * sizeof(blocks_meta_t);
return shards > 1 ? (off + 63) & ~(size_t)63 : off;
}
static inline size_t sbo_header_size(uint8_t shards) {
return sbo_lock_off(shards) + (size_t)shards * sizeof(sbo_lock_t);
}
static inline sbo_lock_t *sbo_pool_lock(sbo_meta_t *meta, uint8_t si) {
return (sbo_lock_t *)((uint8_t *)(meta + 1) + meta->root_slots * sizeof(blocks_meta_t)) + si;
return (sbo_lock_t *)((uint8_t *)meta + sbo_lock_off(meta->root_slots)) + si;
}
static inline uint8_t *sbo_pool_mem(sbo_meta_t *meta, uint8_t si) {
return (uint8_t *)(meta + 1)
+ meta->root_slots * SBO_POOL_HDR
return (uint8_t *)meta + sbo_header_size(meta->root_slots)
+ si * meta->per_slot_meta;
}

Expand Down Expand Up @@ -461,6 +474,7 @@ static inline bool sbo_magic_ok(const sbo_meta_t *meta) {
static inline bool sbo_meta_ok(const sbo_meta_t *meta) {
if (!sbo_magic_ok(meta)) return false;
if (meta->root_slots != 1 && meta->root_slots != SBO_MAX_SHARDS) return false;
if (meta->root_slots > 1 && meta->layout != SBO_LAYOUT_LOCK64) return false;
if (meta->shard_mask != meta->root_slots - 1) return false;
if (meta->slot_shift < 9 || meta->slot_shift >= 64) return false;
if (meta->data_size == 0
Expand Down Expand Up @@ -512,7 +526,7 @@ int sbo_init(void *metaptr, size_t head_size, size_t data_size) {
uint8_t shards = sbo_shards_for_data(data_size);
size_t header_base, per_slot_meta;
for (;;) {
header_base = sizeof(sbo_meta_t) + (size_t)shards * SBO_POOL_HDR;
header_base = sbo_header_size(shards);
if (head_size <= header_base) return -1;
per_slot_meta = ((head_size - header_base) / shards) & ~(size_t)7;
if (shards == 1
Expand All @@ -528,7 +542,8 @@ int sbo_init(void *metaptr, size_t head_size, size_t data_size) {
meta->shard_mask = (uint8_t)(shards - 1);
meta->slot_shift = (uint8_t)__builtin_ctzll(data_size / shards);
meta->per_slot_meta = per_slot_meta;
memset((uint8_t *)(meta + 1), 0, (size_t)shards * SBO_POOL_HDR);
meta->layout = shards > 1 ? SBO_LAYOUT_LOCK64 : 0;
memset((uint8_t *)(meta + 1), 0, header_base - sizeof(*meta));

uint8_t root_level =
(uint8_t)(sbo_align_to(slots / shards).level - 1);
Expand Down Expand Up @@ -728,7 +743,7 @@ void *sbo_data_ptr(void *metaptr, void *data_base, uint64_t obj_offset) {

size_t sbo_meta_size(size_t data_size, size_t per_slot_pool) {
uint8_t shards = sbo_shards_for_data(data_size);
return sizeof(sbo_meta_t) + (size_t)shards * (SBO_POOL_HDR + per_slot_pool);
return sbo_header_size(shards) + (size_t)shards * per_slot_pool;
}

#endif /* SLOTSBOXMALLOC_IMPLEMENTATION */
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