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Fix long spinning in rtree_node_init

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rtree_node_init spinlocks the node, allocates, and then sets the node.
This is under heavy contention at the top of the tree if many threads
start to allocate at the same time.

Instead, take a per-rtree sleeping mutex to reduce spinning.  Tested
both pthreads and osx OSSpinLock, and both reduce spinning adequately

Previous benchmark time:
./ttest1 500 100
~15s

New benchmark time:
./ttest1 500 100
.57s
This commit is contained in:
Dave Watson 2016-10-31 16:23:33 -07:00 • committed by Jason Evans
parent 712fde79fd
commit 25f7bbcf28
4 changed files with 15 additions and 19 deletions
Download patch file Download diff file Expand all files Collapse all files

23
src/rtree.c
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@ -59,6 +59,8 @@ rtree_new(rtree_t *rtree, unsigned bits)
}
rtree->start_level[RTREE_HEIGHT_MAX] = 0;
malloc_mutex_init(&rtree->init_lock, "rtree", WITNESS_RANK_RTREE);
return (false);
}
@ -135,25 +137,18 @@ rtree_node_init(tsdn_t *tsdn, rtree_t *rtree, unsigned level,
{
rtree_elm_t *node;
if (atomic_cas_p((void **)elmp, NULL, RTREE_NODE_INITIALIZING)) {
spin_t spinner;
/*
* Another thread is already in the process of initializing.
* Spin-wait until initialization is complete.
*/
spin_init(&spinner);
do {
spin_adaptive(&spinner);
node = atomic_read_p((void **)elmp);
} while (node == RTREE_NODE_INITIALIZING);
} else {
malloc_mutex_lock(tsdn, &rtree->init_lock);
node = atomic_read_p((void**)elmp);
if (node == NULL) {
node = rtree_node_alloc(tsdn, rtree, ZU(1) <<
rtree->levels[level].bits);
if (node == NULL)
if (node == NULL) {
malloc_mutex_unlock(tsdn, &rtree->init_lock);
return (NULL);
}
atomic_write_p((void **)elmp, node);
}
malloc_mutex_unlock(tsdn, &rtree->init_lock);
return (node);
}