K 10
svn:author
V 3
mjg
K 8
svn:date
V 27
2017-02-08T19:28:46.979962Z
K 7
svn:log
V 230
rwlock: implemenet rlock/runlock fast path

This improves singlethreaded throughput on my test machine from ~247 mln
ops/s to ~328 mln.

It is mostly about avoiding the setup cost of lockstat.

Reviewed by:	jhb (previous version)

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