[lttng-dev] [PATCH 01/12] introduce bucket_at() and improve readability
Lai Jiangshan
laijs at cn.fujitsu.com
Mon Nov 28 03:07:57 EST 2011
Fast path is not changed.
It will slow down very little for slow path.
Signed-off-by: Lai Jiangshan <laijs at cn.fujitsu.com>
---
rculfhash.c | 115 +++++++++++++++++++++++++++++++---------------------------
1 files changed, 61 insertions(+), 54 deletions(-)
diff --git a/rculfhash.c b/rculfhash.c
index 4f82da4..5ad7583 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -756,18 +756,14 @@ unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr,
return old2;
}
-static
-struct cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size,
- unsigned long hash)
+static inline
+struct cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index)
{
- unsigned long index, order;
-
- assert(size > 0);
- index = hash & (size - 1);
+ unsigned long order;
- if (index < ht->min_alloc_size) {
- dbg_printf("lookup hash %lu index %lu order 0 aridx 0\n",
- hash, index);
+ if ((__builtin_constant_p(index) && index == 0)
+ || index < ht->min_alloc_size) {
+ dbg_printf("bucket index %lu order 0 aridx 0\n", index);
return &ht->t.tbl[0]->nodes[index];
}
/*
@@ -776,11 +772,19 @@ struct cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size,
* get_count_order_ulong.
*/
order = fls_ulong(index);
- dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n",
- hash, index, order, index & ((1UL << (order - 1)) - 1));
+ dbg_printf("bucket index %lu order %lu aridx %lu\n",
+ index, order, index & ((1UL << (order - 1)) - 1));
return &ht->t.tbl[order]->nodes[index & ((1UL << (order - 1)) - 1)];
}
+static inline
+struct cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size,
+ unsigned long hash)
+{
+ assert(size > 0);
+ return bucket_at(ht, hash & (size - 1));
+}
+
/*
* Remove all logically deleted nodes from a bucket up to a certain node key.
*/
@@ -1106,19 +1110,18 @@ static
void init_table_populate_partition(struct cds_lfht *ht, unsigned long i,
unsigned long start, unsigned long len)
{
- unsigned long j;
+ unsigned long j, size = 1UL << (i - 1);
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 = &ht->t.tbl[i]->nodes[j];
-
- dbg_printf("init populate: i %lu j %lu hash %lu\n",
- i, j, (1UL << (i - 1)) + j);
- new_node->reverse_hash =
- bit_reverse_ulong((1UL << (i - 1)) + j);
- _cds_lfht_add(ht, NULL, NULL, 1UL << (i - 1),
- new_node, NULL, 1);
+ for (j = size + start; j < size + start + len; j++) {
+ struct cds_lfht_node *new_node = bucket_at(ht, j);
+
+ assert(j >= size && j < (size << 1));
+ dbg_printf("init populate: order %lu index %lu hash %lu\n",
+ i, j, j);
+ new_node->reverse_hash = bit_reverse_ulong(j);
+ _cds_lfht_add(ht, NULL, NULL, size, new_node, NULL, 1);
}
ht->cds_lfht_rcu_read_unlock();
}
@@ -1206,18 +1209,18 @@ static
void remove_table_partition(struct cds_lfht *ht, unsigned long i,
unsigned long start, unsigned long len)
{
- unsigned long j;
+ unsigned long j, size = 1UL << (i - 1);
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 = &ht->t.tbl[i]->nodes[j];
-
- dbg_printf("remove entry: i %lu j %lu hash %lu\n",
- i, j, (1UL << (i - 1)) + j);
- fini_node->reverse_hash =
- bit_reverse_ulong((1UL << (i - 1)) + j);
- (void) _cds_lfht_del(ht, 1UL << (i - 1), fini_node, 1);
+ for (j = size + start; j < size + start + len; j++) {
+ struct cds_lfht_node *fini_node = bucket_at(ht, j);
+
+ assert(j >= size && j < (size << 1));
+ dbg_printf("remove entry: order %lu index %lu hash %lu\n",
+ i, j, j);
+ fini_node->reverse_hash = bit_reverse_ulong(j);
+ (void) _cds_lfht_del(ht, size, fini_node, 1);
}
ht->cds_lfht_rcu_read_unlock();
}
@@ -1294,14 +1297,15 @@ static
void cds_lfht_create_bucket(struct cds_lfht *ht, unsigned long size)
{
struct cds_lfht_node *prev, *node;
- unsigned long order, len, i, j;
+ unsigned long order, len, i;
ht->t.tbl[0] = calloc(1, ht->min_alloc_size * sizeof(struct cds_lfht_node));
assert(ht->t.tbl[0]);
- dbg_printf("create bucket: order %lu index %lu hash %lu\n", 0, 0, 0);
- ht->t.tbl[0]->nodes[0].next = flag_bucket(get_end());
- ht->t.tbl[0]->nodes[0].reverse_hash = 0;
+ dbg_printf("create bucket: order 0 index 0 hash 0\n");
+ node = bucket_at(ht, 0);
+ node->next = flag_bucket(get_end());
+ node->reverse_hash = 0;
for (order = 1; order < get_count_order_ulong(size) + 1; order++) {
len = 1UL << (order - 1);
@@ -1312,22 +1316,28 @@ void cds_lfht_create_bucket(struct cds_lfht *ht, unsigned long size)
assert(ht->t.tbl[order]);
}
- i = 0;
- prev = ht->t.tbl[i]->nodes;
- for (j = 0; j < len; j++) {
- if (j & (j - 1)) { /* Between power of 2 */
- prev++;
- } else if (j) { /* At each power of 2 */
- i++;
- prev = ht->t.tbl[i]->nodes;
- }
+ for (i = 0; i < len; i++) {
+ /*
+ * Now, we are trying to init the node with the
+ * hash=(len+i) (which is also a bucket with the
+ * index=(len+i)) and insert it into the hash table,
+ * so this node has to be inserted after the bucket
+ * with the index=(len+i)&(len-1)=i. And because there
+ * is no other non-bucket node nor bucket node with
+ * larger index/hash inserted, so the bucket node
+ * being inserted should be inserted directly linked
+ * after the bucket node with index=i.
+ */
+ prev = bucket_at(ht, i);
+ node = bucket_at(ht, len + i);
- node = &ht->t.tbl[order]->nodes[j];
dbg_printf("create bucket: order %lu index %lu hash %lu\n",
- order, j, j + len);
+ order, len + i, len + i);
+ node->reverse_hash = bit_reverse_ulong(len + i);
+
+ /* insert after prev */
+ assert(is_bucket(prev->next));
node->next = prev->next;
- assert(is_bucket(node->next));
- node->reverse_hash = bit_reverse_ulong(j + len);
prev->next = flag_bucket(node);
}
}
@@ -1477,14 +1487,11 @@ void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter)
void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter)
{
- struct cds_lfht_node *lookup;
-
/*
* Get next after first bucket node. The first bucket node is the
* first node of the linked list.
*/
- lookup = &ht->t.tbl[0]->nodes[0];
- iter->next = lookup->next;
+ iter->next = bucket_at(ht, 0)->next;
cds_lfht_next(ht, iter);
}
@@ -1570,7 +1577,7 @@ int cds_lfht_delete_bucket(struct cds_lfht *ht)
unsigned long order, i, size;
/* Check that the table is empty */
- node = &ht->t.tbl[0]->nodes[0];
+ node = bucket_at(ht, 0);
do {
node = clear_flag(node)->next;
if (!is_bucket(node))
@@ -1649,7 +1656,7 @@ void cds_lfht_count_nodes(struct cds_lfht *ht,
*removed = 0;
/* Count non-bucket nodes in the table */
- node = &ht->t.tbl[0]->nodes[0];
+ node = bucket_at(ht, 0);
do {
next = rcu_dereference(node->next);
if (is_removed(next)) {
--
1.7.4.4
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