[ltt-dev] [PATCH 03/10 round10] ht->t.size is no required larger than ht->min_table_size now

[Mathieu Desnoyers]

* Lai Jiangshan (laijs at cn.fujitsu.com) wrote:
> Thanks to the wrappers of bucket table alloc/free.

Sorry, I don't understand this change, and I don't see how the patch
below matches the patch title. This patch does not touch ht->t.size at
all, and seems to use MIN_TABLE_SIZE to replace ht->min_table_size, but
does not explain why this is possible.

More below,

> 
> Signed-off-by: Lai Jiangshan <laijs at cn.fujitsu.com>
> ---
>  rculfhash.c            |   19 ++++++++++---------
>  tests/test_urcu_hash.c |    2 +-
>  2 files changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/rculfhash.c b/rculfhash.c
> index c7f993f..a72e1a5 100644
> --- a/rculfhash.c
> +++ b/rculfhash.c
> @@ -186,7 +186,8 @@
>  /*
>   * Define the minimum table size.
>   */
> -#define MIN_TABLE_SIZE			1
> +#define MIN_TABLE_ORDER			0
> +#define MIN_TABLE_SIZE			(1UL << MIN_TABLE_ORDER)
>  
>  #if (CAA_BITS_PER_LONG == 32)
>  #define MAX_TABLE_ORDER			32
> @@ -1141,7 +1142,7 @@ void init_table_populate_partition(struct cds_lfht *ht, unsigned long i,
>  {
>  	unsigned long j, size = 1UL << (i - 1);
>  
> -	assert(i > ht->min_alloc_order);
> +	assert(i > MIN_TABLE_ORDER);

Here, all this does is change the min_alloc_order

>  	ht->cds_lfht_rcu_read_lock();
>  	for (j = start + size; j < size + start + len; j++) {
>  		struct cds_lfht_node *new_node = bucket_at(ht, j);
> @@ -1177,7 +1178,7 @@ void init_table(struct cds_lfht *ht,
>  
>  	dbg_printf("init table: first_order %lu last_order %lu\n",
>  		   first_order, last_order);
> -	assert(first_order > ht->min_alloc_order);
> +	assert(first_order > MIN_TABLE_ORDER);
>  	for (i = first_order; i <= last_order; i++) {
>  		unsigned long len;
>  
> @@ -1239,7 +1240,7 @@ void remove_table_partition(struct cds_lfht *ht, unsigned long i,
>  {
>  	unsigned long j, size = 1UL << (i - 1);
>  
> -	assert(i > ht->min_alloc_order);
> +	assert(i > MIN_TABLE_ORDER);
>  	ht->cds_lfht_rcu_read_lock();
>  	for (j = size + start; j < size + start + len; j++) {
>  		struct cds_lfht_node *fini_node = bucket_at(ht, j);
> @@ -1276,7 +1277,7 @@ void fini_table(struct cds_lfht *ht,
>  
>  	dbg_printf("fini table: first_order %lu last_order %lu\n",
>  		   first_order, last_order);
> -	assert(first_order > ht->min_alloc_order);
> +	assert(first_order > MIN_TABLE_ORDER);
>  	for (i = last_order; i >= first_order; i--) {
>  		unsigned long len;
>  
> @@ -1376,7 +1377,7 @@ struct cds_lfht *_cds_lfht_new(unsigned long init_size,
>  	if (!init_size || (init_size & (init_size - 1)))
>  		return NULL;
>  	min_alloc_size = max(min_alloc_size, MIN_TABLE_SIZE);
> -	init_size = max(init_size, min_alloc_size);
> +	init_size = max(init_size, MIN_TABLE_SIZE);
>  	ht = calloc(1, sizeof(struct cds_lfht));
>  	assert(ht);
>  	ht->flags = flags;
> @@ -1706,7 +1707,7 @@ void _do_cds_lfht_shrink(struct cds_lfht *ht,
>  {
>  	unsigned long old_order, new_order;
>  
> -	new_size = max(new_size, ht->min_alloc_size);
> +	new_size = max(new_size, MIN_TABLE_SIZE);
>  	old_order = get_count_order_ulong(old_size);
>  	new_order = get_count_order_ulong(new_size);
>  	dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
> @@ -1754,7 +1755,7 @@ static
>  void resize_target_update_count(struct cds_lfht *ht,
>  				unsigned long count)
>  {
> -	count = max(count, ht->min_alloc_size);
> +	count = max(count, MIN_TABLE_SIZE);
>  	uatomic_set(&ht->t.resize_target, count);
>  }
>  
> @@ -1829,7 +1830,7 @@ void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
>  {
>  	if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
>  		return;
> -	count = max(count, ht->min_alloc_size);
> +	count = max(count, MIN_TABLE_SIZE);
>  	if (count == size)
>  		return;		/* Already the right size, no resize needed */
>  	if (count > size) {	/* lazy grow */
> diff --git a/tests/test_urcu_hash.c b/tests/test_urcu_hash.c
> index 509767c..b9e3e81 100644
> --- a/tests/test_urcu_hash.c
> +++ b/tests/test_urcu_hash.c
> @@ -896,7 +896,7 @@ int main(int argc, char **argv)
>  		return -1;
>  	}
>  
> -	if (min_hash_alloc_size && min_hash_alloc_size * (min_hash_alloc_size - 1)) {
> +	if (min_hash_alloc_size && min_hash_alloc_size & (min_hash_alloc_size - 1)) {

This seems to fix a bug in the test program, but it's not documented.
Maybe this should go in as a separate patch ?

Thanks,

Mathieu

>  		printf("Error: Min hash alloc size %lu is not a power of 2.\n",
>  			min_hash_alloc_size);
>  		return -1;
> -- 
> 1.7.4.4
> 

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