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

[Mathieu Desnoyers]

"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.

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
> 

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