[ltt-dev] [PATCH 3/7] rculfhash: make cds_lfht_lookup() more generic

[Mathieu Desnoyers]

* Lai Jiangshan (laijs at cn.fujitsu.com) wrote:
> We use hash value to determine the range of the object
> and use cds_lfht_lookup_fct to lookup them.
> 
> Signed-off-by: Lai Jiangshan <laijs at cn.fujitsu.com>
> ---
>  rculfhash.c            |    8 ++++----
>  tests/test_urcu_hash.c |   25 ++++++++++++++++++++++---
>  urcu/rculfhash.h       |    4 +++-
>  3 files changed, 29 insertions(+), 8 deletions(-)
> 
> diff --git a/rculfhash.c b/rculfhash.c
> index d1a1766..29054cd 100644
> --- a/rculfhash.c
> +++ b/rculfhash.c
> @@ -1391,14 +1391,14 @@ struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
>  	return ht;
>  }
>  
> -void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
> +void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
> +		cds_lfht_lookup_fct match, void *arg,

arg -> key ?

for "match", our approach is to provide this function as parameter to
cds_lfht_new rather than pass it as parameter each time a lookup is
performed. What is the reason why we should pass it here as a parameter?

Thanks,

Mathieu

>  		struct cds_lfht_iter *iter)
>  {
>  	struct cds_lfht_node *node, *next, *dummy_node;
>  	struct _cds_lfht_node *lookup;
> -	unsigned long hash, reverse_hash, size;
> +	unsigned long 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);
> @@ -1421,7 +1421,7 @@ void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
>  		if (caa_likely(!is_removed(next))
>  		    && !is_dummy(next)
>  		    && node->p.reverse_hash == reverse_hash
> -		    && caa_likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) {
> +		    && caa_likely(match(node, arg))) {
>  				break;
>  		}
>  		node = clear_flag(next);
> diff --git a/tests/test_urcu_hash.c b/tests/test_urcu_hash.c
> index e28c14a..4c45573 100644
> --- a/tests/test_urcu_hash.c
> +++ b/tests/test_urcu_hash.c
> @@ -41,6 +41,8 @@
>  #define DEFAULT_MIN_ALLOC_SIZE	1
>  #define DEFAULT_RAND_POOL	1000000
>  
> +#define TEST_HASH_SEED	0x42UL
> +
>  /* Make this big enough to include the POWER5+ L3 cacheline size of 256B */
>  #define CACHE_LINE_SIZE 4096
>  
> @@ -419,6 +421,23 @@ unsigned long test_compare(void *key1, size_t key1_len,
>  		return 1;
>  }
>  
> +static
> +int test_match(struct cds_lfht_node *node, void *arg)
> +{
> +	return !test_compare(node->key, node->key_len,
> +			arg, sizeof(unsigned long));
> +}
> +
> +static
> +void cds_lfht_test_lookup(struct cds_lfht *ht, void *key, size_t key_len,
> +		struct cds_lfht_iter *iter)
> +{
> +	assert(key_len == sizeof(unsigned long));
> +
> +	cds_lfht_lookup(ht, test_hash(key, key_len, TEST_HASH_SEED),
> +			test_match, key, iter);
> +}
> +
>  void *thr_count(void *arg)
>  {
>  	printf_verbose("thread_begin %s, thread id : %lx, tid %lu\n",
> @@ -479,7 +498,7 @@ void *thr_reader(void *_count)
>  
>  	for (;;) {
>  		rcu_read_lock();
> -		cds_lfht_lookup(test_ht,
> +		cds_lfht_test_lookup(test_ht,
>  			(void *)(((unsigned long) rand_r(&rand_lookup) % lookup_pool_size) + lookup_pool_offset),
>  			sizeof(void *), &iter);
>  		node = cds_lfht_iter_get_test_node(&iter);
> @@ -574,7 +593,7 @@ void *thr_writer(void *_count)
>  		} else {
>  			/* May delete */
>  			rcu_read_lock();
> -			cds_lfht_lookup(test_ht,
> +			cds_lfht_test_lookup(test_ht,
>  				(void *)(((unsigned long) rand_r(&rand_lookup) % write_pool_size) + write_pool_offset),
>  				sizeof(void *), &iter);
>  			ret = cds_lfht_del(test_ht, &iter);
> @@ -932,7 +951,7 @@ int main(int argc, char **argv)
>  	 * thread from the point of view of resize.
>  	 */
>  	rcu_register_thread();
> -	test_ht = cds_lfht_new(test_hash, test_compare, 0x42UL,
> +	test_ht = cds_lfht_new(test_hash, test_compare, TEST_HASH_SEED,
>  			init_hash_size, min_hash_alloc_size,
>  			(opt_auto_resize ? CDS_LFHT_AUTO_RESIZE : 0) |
>  			CDS_LFHT_ACCOUNTING, NULL);
> diff --git a/urcu/rculfhash.h b/urcu/rculfhash.h
> index f4f3373..b56fe56 100644
> --- a/urcu/rculfhash.h
> +++ b/urcu/rculfhash.h
> @@ -86,6 +86,7 @@ typedef unsigned long (*cds_lfht_hash_fct)(void *key, size_t length,
>  					unsigned long seed);
>  typedef unsigned long (*cds_lfht_compare_fct)(void *key1, size_t key1_len,
>  					void *key2, size_t key2_len);
> +typedef int (*cds_lfht_lookup_fct)(struct cds_lfht_node *node, void *arg);
>  
>  /*
>   * cds_lfht_node_init - initialize a hash table node
> @@ -203,7 +204,8 @@ void cds_lfht_count_nodes(struct cds_lfht *ht,
>   * Call with rcu_read_lock held.
>   * Threads calling this API need to be registered RCU read-side threads.
>   */
> -void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
> +void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
> +		cds_lfht_lookup_fct match, void *arg,
>  		struct cds_lfht_iter *iter);
>  
>  /*
> -- 
> 1.7.4.4
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com