[ltt-dev] [PATCH 6/9] test hash value Confilict with buckets

[laijs@cn.fujitsu.com (Lai Jiangshan)]

On 11/15/2011 07:22 PM, Mathieu Desnoyers wrote:
> "Confilict" -> "conflict"
> 
> This increases conflicts by restricting the pool of random numbers to a
> limited number of bits. Actually, this approach replaces the "pool size"
> parameters I already have there, with slightly less flexibility though.
> Please look into the "random number pool size" to try to achieve the
> same effect.

I missed something? pool size in the original code is constant when the test
is started.

And when the hash table is larger/equal than the pool, many bucket is unused
and cause long chain in a bucket.

> 
> Thanks,
> 
> Mathieu
> 
> * Lai Jiangshan (laijs at cn.fujitsu.com) wrote:
>> Signed-off-by: Lai Jiangshan <laijs at cn.fujitsu.com>
>> ---
>>  tests/test_urcu_hash.c |   20 +++++++++++++++++++-
>>  1 files changed, 19 insertions(+), 1 deletions(-)
>>
>> diff --git a/tests/test_urcu_hash.c b/tests/test_urcu_hash.c
>> index 02d2c63..eb42522 100644
>> --- a/tests/test_urcu_hash.c
>> +++ b/tests/test_urcu_hash.c
>> @@ -141,6 +141,7 @@ static unsigned long min_hash_alloc_size = DEFAULT_MIN_ALLOC_SIZE;
>>  static unsigned long init_populate;
>>  static int opt_auto_resize;
>>  static int add_only, add_unique, add_replace;
>> +static int opt_test_bucket_conflict;
>>  
>>  static int count_pipe[2];
>>  
>> @@ -390,8 +391,22 @@ int lookup_first(struct cds_lfht_node *node, void *key)
>>  static inline
>>  void lfht_test_node_init(struct lfht_test_node *node)
>>  {
>> +	unsigned long hash = test_rand_get();
>> +
>>  	cds_lfht_node_init(&node->node);
>> -	node->hash = test_rand_get();
>> +
>> +	if (opt_test_bucket_conflict) {
>> +#if (CAA_BITS_PER_LONG == 32)
>> +		int hash_bits= test_rand_get_bits(5);
>> +#else
>> +		int hash_bits= test_rand_get_bits(6);
>> +#endif
>> +
>> +		if (hash_bits > 4)
>> +			hash &= (1UL << hash_bits) - 1;
>> +	}
>> +
>> +	node->hash = hash;
>>  }
>>  
>>  static
>> @@ -674,6 +689,7 @@ void show_usage(int argc, char **argv)
>>  	printf("        [-i] Add only (no removal).\n");
>>  	printf("        [-k nr_nodes] Number of nodes to insert initially.\n");
>>  	printf("        [-A] Automatically resize hash table.\n");
>> +	printf("	[-C] Use some hash value Confilict with buckets.\n");
>>  	printf("\n\n");
>>  }
>>  
>> @@ -792,6 +808,8 @@ int main(int argc, char **argv)
>>  		case 'A':
>>  			opt_auto_resize = 1;
>>  			break;
>> +		case 'C':
>> +			opt_test_bucket_conflict = 1;
>>  			break;
>>  
>>  		}
>> -- 
>> 1.7.4.4
>>
>