Avoid alloc small memory pieces

Add min_alloc_size (minimum allocation size) for allocation.

Now we can gain better cache locality by specifying larger minimum
allocation size.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/rculfhash.c b/rculfhash.c
index 0bcbb1e832a5ab41c4d4357c0dafa4ff87832db7..675ef382311beafcbb8d62ad284b2032d6db79aa 100644 (file)
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -241,6 +241,8 @@ struct cds_lfht {
        struct rcu_table t;
        cds_lfht_hash_fct hash_fct;
        cds_lfht_compare_fct compare_fct;
+       unsigned long min_alloc_order;
+       unsigned long min_alloc_size;
        unsigned long hash_seed;
        int flags;
        /*
@@ -1078,7 +1080,7 @@ void init_table_populate_partition(struct cds_lfht *ht, unsigned long i,
 {
        unsigned long j;
 
-       assert(i > 0);
+       assert(i > ht->min_alloc_order);
        ht->cds_lfht_rcu_read_lock();
        for (j = start; j < start + len; j++) {
                struct cds_lfht_node *new_node =
@@ -1116,7 +1118,7 @@ void init_table(struct cds_lfht *ht,
 
        dbg_printf("init table: first_order %lu last_order %lu\n",
                   first_order, last_order);
-       assert(first_order > 0);
+       assert(first_order > ht->min_alloc_order);
        for (i = first_order; i <= last_order; i++) {
                unsigned long len;
 
@@ -1179,7 +1181,7 @@ void remove_table_partition(struct cds_lfht *ht, unsigned long i,
 {
        unsigned long j;
 
-       assert(i > 0);
+       assert(i > ht->min_alloc_order);
        ht->cds_lfht_rcu_read_lock();
        for (j = start; j < start + len; j++) {
                struct cds_lfht_node *fini_node =
@@ -1217,7 +1219,7 @@ void fini_table(struct cds_lfht *ht,
 
        dbg_printf("fini table: first_order %lu last_order %lu\n",
                   first_order, last_order);
-       assert(first_order > 0);
+       assert(first_order > ht->min_alloc_order);
        for (i = last_order; i >= first_order; i--) {
                unsigned long len;
 
@@ -1268,7 +1270,7 @@ void cds_lfht_create_dummy(struct cds_lfht *ht, unsigned long size)
        struct _cds_lfht_node *prev, *node;
        unsigned long order, len, i, j;
 
-       ht->t.tbl[0] = calloc(1, sizeof(struct _cds_lfht_node));
+       ht->t.tbl[0] = calloc(1, ht->min_alloc_size * sizeof(struct _cds_lfht_node));
        assert(ht->t.tbl[0]);
 
        dbg_printf("create dummy: order %lu index %lu hash %lu\n", 0, 0, 0);
@@ -1277,8 +1279,12 @@ void cds_lfht_create_dummy(struct cds_lfht *ht, unsigned long size)
 
        for (order = 1; order < get_count_order_ulong(size) + 1; order++) {
                len = 1UL << (order - 1);
-               ht->t.tbl[order] = calloc(1, len * sizeof(struct _cds_lfht_node));
-               assert(ht->t.tbl[order]);
+               if (order <= ht->min_alloc_order) {
+                       ht->t.tbl[order] = (void *)(ht->t.tbl[0]->nodes + len);
+               } else {
+                       ht->t.tbl[order] = calloc(1, len * sizeof(struct _cds_lfht_node));
+                       assert(ht->t.tbl[order]);
+               }
 
                i = 0;
                prev = ht->t.tbl[i]->nodes;
@@ -1305,6 +1311,7 @@ struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
                        cds_lfht_compare_fct compare_fct,
                        unsigned long hash_seed,
                        unsigned long init_size,
+                       unsigned long min_alloc_size,
                        int flags,
                        void (*cds_lfht_call_rcu)(struct rcu_head *head,
                                        void (*func)(struct rcu_head *head)),
@@ -1320,9 +1327,14 @@ struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
        struct cds_lfht *ht;
        unsigned long order;
 
+       /* min_alloc_size must be power of two */
+       if (!min_alloc_size || (min_alloc_size & (min_alloc_size - 1)))
+               return NULL;
        /* init_size must be power of two */
-       if (init_size && (init_size & (init_size - 1)))
+       if (!init_size || (init_size & (init_size - 1)))
                return NULL;
+       min_alloc_size = max(min_alloc_size, MIN_TABLE_SIZE);
+       init_size = max(init_size, min_alloc_size);
        ht = calloc(1, sizeof(struct cds_lfht));
        assert(ht);
        ht->hash_fct = hash_fct;
@@ -1341,10 +1353,12 @@ struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
        /* this mutex should not nest in read-side C.S. */
        pthread_mutex_init(&ht->resize_mutex, NULL);
        ht->flags = flags;
-       order = get_count_order_ulong(max(init_size, MIN_TABLE_SIZE));
+       order = get_count_order_ulong(init_size);
        ht->t.resize_target = 1UL << order;
        cds_lfht_create_dummy(ht, 1UL << order);
        ht->t.size = 1UL << order;
+       ht->min_alloc_size = min_alloc_size;
+       ht->min_alloc_order = get_count_order_ulong(min_alloc_size);
        return ht;
 }
 
@@ -1562,7 +1576,12 @@ int cds_lfht_delete_dummy(struct cds_lfht *ht)
                                bit_reverse_ulong(ht->t.tbl[order]->nodes[i].reverse_hash));
                        assert(is_dummy(ht->t.tbl[order]->nodes[i].next));
                }
-               poison_free(ht->t.tbl[order]);
+
+               if (order == ht->min_alloc_order)
+                       poison_free(ht->t.tbl[0]);
+               else if (order > ht->min_alloc_order)
+                       poison_free(ht->t.tbl[order]);
+               /* Nothing to delete for order < ht->min_alloc_order */
        }
        return 0;
 }
@@ -1663,7 +1682,7 @@ void _do_cds_lfht_shrink(struct cds_lfht *ht,
 {
        unsigned long old_order, new_order;
 
-       new_size = max(new_size, MIN_TABLE_SIZE);
+       new_size = max(new_size, ht->min_alloc_size);
        old_order = get_count_order_ulong(old_size);
        new_order = get_count_order_ulong(new_size);
        dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
@@ -1713,7 +1732,7 @@ static
 void resize_target_update_count(struct cds_lfht *ht,
                                unsigned long count)
 {
-       count = max(count, MIN_TABLE_SIZE);
+       count = max(count, ht->min_alloc_size);
        uatomic_set(&ht->t.resize_target, count);
 }
 

diff --git a/tests/test_urcu_hash.c b/tests/test_urcu_hash.c
index db45c8c389801a3af5a40dfc58c3e2a492172dc0..70db8b3ca750f398f7314c9a6b794b3140d1bd20 100644 (file)
--- a/tests/test_urcu_hash.c
+++ b/tests/test_urcu_hash.c
@@ -888,7 +888,7 @@ int main(int argc, char **argv)
         */
        rcu_register_thread();
        test_ht = cds_lfht_new(test_hash, test_compare, 0x42UL,
-                       init_hash_size,
+                       init_hash_size, 1,
                        opt_auto_resize ? CDS_LFHT_AUTO_RESIZE : 0, NULL);
        ret = populate_hash();
        assert(!ret);

diff --git a/urcu/rculfhash.h b/urcu/rculfhash.h
index 1376b5a0b4e2b4fb0fe70378f9bc91644a845027..fd67b6b892654d7051ed97ddf442289ee824af11 100644 (file)
--- a/urcu/rculfhash.h
+++ b/urcu/rculfhash.h
@@ -103,6 +103,7 @@ struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
                        cds_lfht_compare_fct compare_fct,
                        unsigned long hash_seed,
                        unsigned long init_size,
+                       unsigned long min_alloc_size,
                        int flags,
                        void (*cds_lfht_call_rcu)(struct rcu_head *head,
                                void (*func)(struct rcu_head *head)),
@@ -121,6 +122,7 @@ struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
  * @compare_fct: the key comparison function.
  * @hash_seed: the seed for hash function.
  * @init_size: number of nodes to allocate initially. Must be power of two.
+ * @min_alloc_size: the smallest allocation size to use. Must be power of two.
  * @flags: hash table creation flags (can be combined with bitwise or: '|').
  *           0: no flags.
  *           CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
@@ -143,11 +145,12 @@ struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
                        cds_lfht_compare_fct compare_fct,
                        unsigned long hash_seed,
                        unsigned long init_size,
+                       unsigned long min_alloc_size,
                        int flags,
                        pthread_attr_t *attr)
 {
        return _cds_lfht_new(hash_fct, compare_fct, hash_seed,
-                       init_size, flags,
+                       init_size, min_alloc_size, flags,
                        call_rcu, synchronize_rcu, rcu_read_lock,
                        rcu_read_unlock, rcu_thread_offline,
                        rcu_thread_online, rcu_register_thread,