tree aa27872a941e3e5d47a6da51d59da53fe018afe5
parent 712fde79fda767ce1eec7cf1c967feeae90b0c21
author Dave Watson <davejwatson@fb.com> 1477956213 -0700
committer Jason Evans <jasone@canonware.com> 1478143853 -0700

Fix long spinning in rtree_node_init

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