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Compact dbuf/buf hashes and lock arrays. #12289

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Merged
merged 1 commit into from
Jul 1, 2021
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Compact dbuf/buf hashes and lock arrays. #12289

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4 changes: 2 additions & 2 deletions include/sys/dbuf.h
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Original file line number Diff line number Diff line change
Expand Up @@ -322,12 +322,12 @@ typedef struct dmu_buf_impl {
} dmu_buf_impl_t;

/* Note: the dbuf hash table is exposed only for the mdb module */
#define DBUF_MUTEXES 8192
#define DBUF_MUTEXES 2048
#define DBUF_HASH_MUTEX(h, idx) (&(h)->hash_mutexes[(idx) & (DBUF_MUTEXES-1)])
typedef struct dbuf_hash_table {
uint64_t hash_table_mask;
dmu_buf_impl_t **hash_table;
kmutex_t hash_mutexes[DBUF_MUTEXES];
kmutex_t hash_mutexes[DBUF_MUTEXES] ____cacheline_aligned;
} dbuf_hash_table_t;

typedef void (*dbuf_prefetch_fn)(void *, boolean_t);
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25 changes: 6 additions & 19 deletions module/zfs/arc.c
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Expand Up @@ -740,29 +740,18 @@ taskq_t *arc_prune_taskq;
* Hash table routines
*/

#define HT_LOCK_ALIGN 64
#define HT_LOCK_PAD (P2NPHASE(sizeof (kmutex_t), (HT_LOCK_ALIGN)))

struct ht_lock {
kmutex_t ht_lock;
#ifdef _KERNEL
unsigned char pad[HT_LOCK_PAD];
#endif
};

#define BUF_LOCKS 8192
#define BUF_LOCKS 2048
typedef struct buf_hash_table {
uint64_t ht_mask;
arc_buf_hdr_t **ht_table;
struct ht_lock ht_locks[BUF_LOCKS];
kmutex_t ht_locks[BUF_LOCKS] ____cacheline_aligned;
} buf_hash_table_t;

static buf_hash_table_t buf_hash_table;

#define BUF_HASH_INDEX(spa, dva, birth) \
(buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
#define BUF_HASH_LOCK(idx) (&buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
#define HDR_LOCK(hdr) \
(BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))

Expand Down Expand Up @@ -1111,7 +1100,7 @@ buf_fini(void)
(buf_hash_table.ht_mask + 1) * sizeof (void *));
#endif
for (i = 0; i < BUF_LOCKS; i++)
mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
mutex_destroy(BUF_HASH_LOCK(i));
kmem_cache_destroy(hdr_full_cache);
kmem_cache_destroy(hdr_full_crypt_cache);
kmem_cache_destroy(hdr_l2only_cache);
Expand Down Expand Up @@ -1276,10 +1265,8 @@ buf_init(void)
for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
*ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);

for (i = 0; i < BUF_LOCKS; i++) {
mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
NULL, MUTEX_DEFAULT, NULL);
}
for (i = 0; i < BUF_LOCKS; i++)
mutex_init(BUF_HASH_LOCK(i), NULL, MUTEX_DEFAULT, NULL);
}

#define ARC_MINTIME (hz>>4) /* 62 ms */
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6 changes: 3 additions & 3 deletions module/zfs/dbuf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -825,12 +825,12 @@ dbuf_init(void)
int i;

/*
* The hash table is big enough to fill all of physical memory
* The hash table is big enough to fill one eighth of physical memory
* with an average block size of zfs_arc_average_blocksize (default 8K).
* By default, the table will take up
* totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
*/
while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE)
while (hsize * zfs_arc_average_blocksize < arc_all_memory() / 8)
hsize <<= 1;

retry:
Expand Down Expand Up @@ -3054,8 +3054,8 @@ dbuf_create(dnode_t *dn, uint8_t level, uint64_t blkid,
db->db_state = DB_EVICTING; /* not worth logging this state change */
if ((odb = dbuf_hash_insert(db)) != NULL) {
/* someone else inserted it first */
kmem_cache_free(dbuf_kmem_cache, db);
mutex_exit(&dn->dn_dbufs_mtx);
kmem_cache_free(dbuf_kmem_cache, db);
DBUF_STAT_BUMP(hash_insert_race);
return (odb);
}
Expand Down