On 10/14/2011 10:12 PM, Mathieu Desnoyers wrote:
> * Lai Jiangshan ([email protected]) wrote:
>> Signed-off-by: Lai Jiangshan <[email protected]>
>> ---
>> rculfhash.c | 47 +++++++++++++++++++++--------------------------
>> 1 files changed, 21 insertions(+), 26 deletions(-)
>>
>> diff --git a/rculfhash.c b/rculfhash.c
>> index 49f3637..1c859ed 100644
>> --- a/rculfhash.c
>> +++ b/rculfhash.c
>> @@ -711,6 +711,22 @@ unsigned long _uatomic_max(unsigned long *ptr, unsigned
>> long v)
>> return v;
>> }
>>
>> +static
>> +struct _cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long
>> size,
>> + unsigned long hash)
>> +{
>> + unsigned long index, order;
>> +
>> + assert(size > 0);
>> + index = hash & (size - 1);
>> + order = get_count_order_ulong(index + 1);
>> +
>> + dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n",
>> + hash, index, order, index & (!order ? 0 : ((1UL << (order -
>> 1)) - 1)));
>> +
>> + return &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order -
>> 1)) - 1))];
>> +}
>> +
>> /*
>> * Remove all logically deleted nodes from a bucket up to a certain node
>> key.
>> */
>> @@ -767,7 +783,6 @@ int _cds_lfht_replace(struct cds_lfht *ht, unsigned long
>> size,
>> struct cds_lfht_node *dummy, *old_next;
>> struct _cds_lfht_node *lookup;
>> int flagged = 0;
>> - unsigned long hash, index, order;
>>
>> if (!old_node) /* Return -ENOENT if asked to replace NULL node */
>> goto end;
>> @@ -812,11 +827,7 @@ int _cds_lfht_replace(struct cds_lfht *ht, unsigned
>> long size,
>> * lookup for the node, and remove it (along with any other
>> * logically removed node) if found.
>> */
>> - hash = bit_reverse_ulong(old_node->p.reverse_hash);
>> - assert(size > 0);
>> - index = hash & (size - 1);
>> - order = get_count_order_ulong(index + 1);
>> - lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order
>> - 1)) - 1))];
>> + lookup = lookup_bucket(ht, size,
>> bit_reverse_ulong(old_node->p.reverse_hash));
>> dummy = (struct cds_lfht_node *) lookup;
>> _cds_lfht_gc_bucket(dummy, new_node);
>> end:
>> @@ -841,7 +852,6 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
>> struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
>> *dummy_node, *return_node;
>> struct _cds_lfht_node *lookup;
>> - unsigned long hash, index, order;
>>
>> assert(!is_dummy(node));
>> assert(!is_removed(node));
>> @@ -850,7 +860,7 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
>> node->p.next = flag_dummy(get_end());
>> return node; /* Initial first add (head) */
>> }
>> - hash = bit_reverse_ulong(node->p.reverse_hash);
>> + lookup = lookup_bucket(ht, size,
>> bit_reverse_ulong(node->p.reverse_hash));
>> for (;;) {
>> uint32_t chain_len = 0;
>>
>> @@ -858,9 +868,6 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
>> * iter_prev points to the non-removed node prior to the
>> * insert location.
>> */
>> - index = hash & (size - 1);
>> - order = get_count_order_ulong(index + 1);
>> - lookup = &ht->t.tbl[order]->nodes[index & ((!order ? 0 : (1UL
>> << (order - 1))) - 1)];
>
> There is a reason why the lookup bucket is done in the loop and in the
> gc_end path below: it deals with concurrent hash table resizes. So I
> agree that merging these code paths into lookup_bucket is good, but I
> think you are changing the behavior here.
>
> Or maybe you have something else in mind that guarantees that the change
> you do here is correct ?
hash and size are constant here,
so the lookup can be moved up.
>
> Thanks,
>
> Mathieu
>
>> iter_prev = (struct cds_lfht_node *) lookup;
>> /* We can always skip the dummy node initially */
>> iter = rcu_dereference(iter_prev->p.next);
>> @@ -936,9 +943,6 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
>> }
>> gc_end:
>> /* Garbage collect logically removed nodes in the bucket */
>> - index = hash & (size - 1);
>> - order = get_count_order_ulong(index + 1);
>> - lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order
>> - 1)) - 1))];
>> dummy_node = (struct cds_lfht_node *) lookup;
>> _cds_lfht_gc_bucket(dummy_node, node);
>> end:
>> @@ -953,7 +957,6 @@ int _cds_lfht_del(struct cds_lfht *ht, unsigned long
>> size,
>> struct cds_lfht_node *dummy, *next, *old;
>> struct _cds_lfht_node *lookup;
>> int flagged = 0;
>> - unsigned long hash, index, order;
>>
>> if (!node) /* Return -ENOENT if asked to delete NULL node */
>> goto end;
>> @@ -984,11 +987,7 @@ int _cds_lfht_del(struct cds_lfht *ht, unsigned long
>> size,
>> * the node, and remove it (along with any other logically removed node)
>> * if found.
>> */
>> - hash = bit_reverse_ulong(node->p.reverse_hash);
>> - assert(size > 0);
>> - index = hash & (size - 1);
>> - order = get_count_order_ulong(index + 1);
>> - lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order
>> - 1)) - 1))];
>> + lookup = lookup_bucket(ht, size,
>> bit_reverse_ulong(node->p.reverse_hash));
>> dummy = (struct cds_lfht_node *) lookup;
>> _cds_lfht_gc_bucket(dummy, node);
>> end:
>> @@ -1313,17 +1312,13 @@ void cds_lfht_lookup(struct cds_lfht *ht, void *key,
>> size_t key_len,
>> {
>> struct cds_lfht_node *node, *next, *dummy_node;
>> struct _cds_lfht_node *lookup;
>> - unsigned long hash, reverse_hash, index, order, size;
>> + unsigned long hash, reverse_hash, size;
>>
>> hash = ht->hash_fct(key, key_len, ht->hash_seed);
>> reverse_hash = bit_reverse_ulong(hash);
>>
>> size = rcu_dereference(ht->t.size);
>> - index = hash & (size - 1);
>> - order = get_count_order_ulong(index + 1);
>> - lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order
>> - 1))) - 1)];
>> - dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n",
>> - hash, index, order, index & (!order ? 0 : ((1UL << (order -
>> 1)) - 1)));
>> + lookup = lookup_bucket(ht, size, hash);
>> dummy_node = (struct cds_lfht_node *) lookup;
>> /* We can always skip the dummy node initially */
>> node = rcu_dereference(dummy_node->p.next);
>> --
>> 1.7.4.4
>>
>
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