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

[Lai Jiangshan]

On 11/22/2011 06:06 PM, Mathieu Desnoyers wrote:
> * 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.
> 

Original code always ensure ht->t.size >= ht->min_table_size.
It is not good, ht->min_table_size should be used for allocation,
not for the bucket size in used.

Thanks,
Lai

Add:
Original code don't do special alloc/free when ht->t.size < ht->min_table_size
in init_table()/fini_table(), so we have to force ht->t.size >= ht->min_table_size.

New code use the wrappers, they handle the special cases.



> 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
>>
>