Hi, A few months ago, I added a patch to inferno-npe to use LOCK XADD instead of the current lock/add/unlock sequence for incref and decref: (http://code.google.com/p/inferno-npe/source/detail?r=b83540e1e77e62a19cbd21d2eb54d43d338716a5 and http://code.google.com/p/inferno-npe/source/detail?r=82f13e6755218ecb7dec0f1392b2eb8bfe0bb2c7). On a 2.66 GHz Core 2 Duo, we noticed a full 14% reduction in runtime (9.6s vs 11.2s) of the thread-ring test. Similar performance gains were noticed on a Core i7 machine, but I no longer have the numbers handy.
Perhaps this change is interesting for Plan 9... -- vs
