Merged as:
commit c1888f3a47cf8f7c213269888ce42d191de7e34a
Author: Mathieu Desnoyers <[email protected]>
Date: Sun Dec 4 10:40:01 2011 -0500
rculfhash: default mm type
In the original patch from Lai Jiangshan <[email protected]>:
When I test backend with the following commands.
(my box is x86_64 with 4 cores/logic cpus)
**(test with Load factor = 100% only)**
./tests/test_urcu_hash 4 0 10 -B mmap -h $((1<<19)) -p $((1<<19))
./tests/test_urcu_hash 4 0 10 -B mmap -h $((1<<18)) -p $((1<<18))
./tests/test_urcu_hash 4 0 10 -B mmap -h $((1<<17)) -p $((1<<17))
./tests/test_urcu_hash 4 0 10 -B mmap -h $((1<<16)) -p $((1<<16))
4readers/no writer
It shows that mmap backend is about 6% better over order backend.
(It also shows that chunk backend is (worse than)/(the same as) order
backend for small/large min_nr_alloc_buckets. (use -m when test)).
Note:
"6%" and the google-perftools told us the bucket_at() is not the
critical bottleneck.
new strategy:
* infinite buckets size --> order mm
* otherwise if 64bits,
with number of buckets <= (1 << 32) --> mmap mm
* otherwise --> order mm
Signed-off-by: Mathieu Desnoyers <[email protected]>
diff --git a/rculfhash.c b/rculfhash.c
index 6c648f1..5ef2c78 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -1271,6 +1271,36 @@ struct cds_lfht *_cds_lfht_new(unsigned long init_size,
if (!init_size || (init_size & (init_size - 1)))
return NULL;
+ /*
+ * Memory management plugin default.
+ */
+ if (!mm) {
+ if (!max_nr_buckets) {
+ /*
+ * If the maximum number of buckets is not
+ * specified, we cannot use the mmap allocator,
+ * so fallback on order allocator.
+ */
+ mm = &cds_lfht_mm_order;
+ } else if (CAA_BITS_PER_LONG > 32
+ && max_nr_buckets <= (1ULL << 32)) {
+ /*
+ * For 64-bit architectures, with max number of
+ * buckets small enough not to use the entire
+ * 64-bit memory mapping space (and allowing a
+ * fair number of hash table instances), use the
+ * mmap allocator, which is faster than the
+ * order allocator.
+ */
+ mm = &cds_lfht_mm_mmap;
+ } else {
+ /*
+ * The fallback is to use the order allocator.
+ */
+ mm = &cds_lfht_mm_order;
+ }
+ }
+
/* max_nr_buckets == 0 for order based mm means infinite */
if (mm == &cds_lfht_mm_order && !max_nr_buckets)
max_nr_buckets = 1UL << (MAX_TABLE_ORDER - 1);
diff --git a/urcu/rculfhash.h b/urcu/rculfhash.h
index 6ed7c8c..de31526 100644
--- a/urcu/rculfhash.h
+++ b/urcu/rculfhash.h
@@ -154,7 +154,7 @@ struct cds_lfht *cds_lfht_new(unsigned long init_size,
pthread_attr_t *attr)
{
return _cds_lfht_new(init_size, min_nr_alloc_buckets, max_nr_buckets,
- flags, &cds_lfht_mm_order, &rcu_flavor, attr);
+ flags, NULL, &rcu_flavor, attr);
}
/*
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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