[ltt-dev] [PATCH 05/10 round10] add max_size arguemnt

[compudj@krystal.dyndns.org (Mathieu Desnoyers)]

* Lai Jiangshan (laijs at cn.fujitsu.com) wrote:
> On 11/22/2011 06:11 PM, Mathieu Desnoyers wrote:
> > arguemnt -> argument
> > 
> > I think we need to discuss the semantic of max_size: here, you propose
> > that max_size is just the number of buckets, but it does not limit the
> > ability of the table to contain more elements than max_size.
> > 
> > IMHO, it would be nice to have max_size limit the number of elements
> > that the table can accept, e.g. ensuring that insertion fails if the
> > number of elements gets over the max_size threshold. It might not need
> > to be an exact thing though, just giving an approximated upper limit
> > might be fine (using the split-counters), as long as it is documented.
> 
> documented: "max_size: the max size of buckets for future growing"
> 
> Is max_bucket_size better?
> and min_alloc_size need to be changed to min_alloc_bucket_size?
> 
> I'm not planing to add "max_size" for the number of elements in this
> round or near future.

maybe max_nr_buckets then ?

nr_ seems to be more descriptive than "size" in this context, because
"size" could lead to some confusion, leading to think that we would be
specifying the size of a bucket rather than actually specifying the
number of buckets. Seems reasonable ?

Thanks,

Mathieu

> 
> Thanks,
> Lai
> 
> > 
> > Thanks,
> > 
> > Mathieu
> > 
> > * Lai Jiangshan (laijs at cn.fujitsu.com) wrote:
> >> Signed-off-by: Lai Jiangshan <laijs at cn.fujitsu.com>
> >> ---
> >>  rculfhash.c            |   17 +++++++++++++++++
> >>  tests/test_urcu_hash.c |    2 +-
> >>  urcu/rculfhash.h       |    9 ++++++---
> >>  3 files changed, 24 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/rculfhash.c b/rculfhash.c
> >> index 2df133c..b7be893 100644
> >> --- a/rculfhash.c
> >> +++ b/rculfhash.c
> >> @@ -266,6 +266,7 @@ struct cds_lfht {
> >>  	struct rcu_table t;
> >>  	unsigned long min_alloc_order;
> >>  	unsigned long min_alloc_size;
> >> +	unsigned long max_size;
> >>  	int flags;
> >>  	/*
> >>  	 * We need to put the work threads offline (QSBR) when taking this
> >> @@ -1351,6 +1352,7 @@ void cds_lfht_create_bucket(struct cds_lfht *ht, unsigned long size)
> >>  
> >>  struct cds_lfht *_cds_lfht_new(unsigned long init_size,
> >>  			unsigned long min_alloc_size,
> >> +			unsigned long max_size,
> >>  			int flags,
> >>  			void (*cds_lfht_call_rcu)(struct rcu_head *head,
> >>  					void (*func)(struct rcu_head *head)),
> >> @@ -1369,11 +1371,22 @@ struct cds_lfht *_cds_lfht_new(unsigned long init_size,
> >>  	/* min_alloc_size must be power of two */
> >>  	if (!min_alloc_size || (min_alloc_size & (min_alloc_size - 1)))
> >>  		return NULL;
> >> +
> >>  	/* init_size must be power of two */
> >>  	if (!init_size || (init_size & (init_size - 1)))
> >>  		return NULL;
> >> +
> >> +	if (!max_size)
> >> +		max_size = 1UL << (MAX_TABLE_ORDER - 1);
> >> +
> >> +	/* max_size must be power of two */
> >> +	if (!max_size || (max_size & (max_size - 1)))
> >> +		return NULL;
> >> +
> >>  	min_alloc_size = max(min_alloc_size, MIN_TABLE_SIZE);
> >>  	init_size = max(init_size, MIN_TABLE_SIZE);
> >> +	max_size = max(max_size, min_alloc_size);
> >> +	init_size = min(init_size, max_size);
> >>  	ht = calloc(1, sizeof(struct cds_lfht));
> >>  	assert(ht);
> >>  	ht->flags = flags;
> >> @@ -1393,6 +1406,7 @@ struct cds_lfht *_cds_lfht_new(unsigned long init_size,
> >>  	ht->t.resize_target = 1UL << order;
> >>  	ht->min_alloc_size = min_alloc_size;
> >>  	ht->min_alloc_order = get_count_order_ulong(min_alloc_size);
> >> +	ht->max_size = max_size;
> >>  	cds_lfht_create_bucket(ht, 1UL << order);
> >>  	ht->t.size = 1UL << order;
> >>  	return ht;
> >> @@ -1752,6 +1766,7 @@ void resize_target_update_count(struct cds_lfht *ht,
> >>  				unsigned long count)
> >>  {
> >>  	count = max(count, MIN_TABLE_SIZE);
> >> +	count = min(count, ht->max_size);
> >>  	uatomic_set(&ht->t.resize_target, count);
> >>  }
> >>  
> >> @@ -1809,6 +1824,7 @@ void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int grow
> >>  {
> >>  	unsigned long target_size = size << growth;
> >>  
> >> +	target_size = min(target_size, ht->max_size);
> >>  	if (resize_target_grow(ht, target_size) >= target_size)
> >>  		return;
> >>  
> >> @@ -1827,6 +1843,7 @@ void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
> >>  	if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
> >>  		return;
> >>  	count = max(count, MIN_TABLE_SIZE);
> >> +	count = min(count, ht->max_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 b9e3e81..2961177 100644
> >> --- a/tests/test_urcu_hash.c
> >> +++ b/tests/test_urcu_hash.c
> >> @@ -967,7 +967,7 @@ int main(int argc, char **argv)
> >>  	 * thread from the point of view of resize.
> >>  	 */
> >>  	rcu_register_thread();
> >> -	test_ht = cds_lfht_new(init_hash_size, min_hash_alloc_size,
> >> +	test_ht = cds_lfht_new(init_hash_size, min_hash_alloc_size, (1UL << 18),
> >>  			(opt_auto_resize ? CDS_LFHT_AUTO_RESIZE : 0) |
> >>  			CDS_LFHT_ACCOUNTING, NULL);
> >>        	ret = populate_hash();
> >> diff --git a/urcu/rculfhash.h b/urcu/rculfhash.h
> >> index c13d3df..2eefd2c 100644
> >> --- a/urcu/rculfhash.h
> >> +++ b/urcu/rculfhash.h
> >> @@ -98,6 +98,7 @@ enum {
> >>   */
> >>  struct cds_lfht *_cds_lfht_new(unsigned long init_size,
> >>  			unsigned long min_alloc_size,
> >> +			unsigned long max_size,
> >>  			int flags,
> >>  			void (*cds_lfht_call_rcu)(struct rcu_head *head,
> >>  				void (*func)(struct rcu_head *head)),
> >> @@ -112,8 +113,9 @@ struct cds_lfht *_cds_lfht_new(unsigned long init_size,
> >>  
> >>  /*
> >>   * cds_lfht_new - allocate a hash table.
> >> - * @init_size: number of nodes to allocate initially. Must be power of two.
> >> - * @min_alloc_size: the smallest allocation size to use. Must be power of two.
> >> + * @init_size: number of buckets to allocate initially. Must be power of two.
> >> + * @min_alloc_size: the smallest allocation buckets size to use. Must be power of two.
> >> + * @max_size: the max size of buckets for future growing. Must be power of two.
> >>   * @flags: hash table creation flags (can be combined with bitwise or: '|').
> >>   *           0: no flags.
> >>   *           CDS_LFHT_AUTO_RESIZE: automatically resize hash table.
> >> @@ -134,10 +136,11 @@ struct cds_lfht *_cds_lfht_new(unsigned long init_size,
> >>  static inline
> >>  struct cds_lfht *cds_lfht_new(unsigned long init_size,
> >>  			unsigned long min_alloc_size,
> >> +			unsigned long max_size,
> >>  			int flags,
> >>  			pthread_attr_t *attr)
> >>  {
> >> -	return _cds_lfht_new(init_size, min_alloc_size, flags,
> >> +	return _cds_lfht_new(init_size, min_alloc_size, max_size, flags,
> >>  			call_rcu, synchronize_rcu, rcu_read_lock,
> >>  			rcu_read_unlock, rcu_thread_offline,
> >>  			rcu_thread_online, rcu_register_thread,
> >> -- 
> >> 1.7.4.4
> >>
> > 
> 
> 
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-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com