The test is just a repeated TestGenericKeyedObjectPool.testThreaded1 with removed sleep in TestThread to maximize contention.

------------------------

JDK6, 20 threads, 50000 loops:

previous:
time: 2359ms
time: 1922ms
time: 1907ms
time: 1921ms
time: 1875ms
time: 1860ms
time: 1922ms
time: 1859ms
time: 1922ms
time: 2000ms

relaxed:
time: 1687ms
time: 1891ms
time: 1859ms
time: 1750ms
time: 1813ms
time: 1797ms
time: 1609ms
time: 1656ms
time: 1719ms
time: 1547ms

------------------------

JDK6, 50 threads, 50000 loops:

previous:
time: 5985ms
time: 5781ms
time: 5250ms
time: 5797ms
time: 5031ms
time: 5391ms
time: 5562ms
time: 4906ms
time: 4750ms
time: 4750ms

relaxed:
time: 4266ms
time: 4297ms
time: 4390ms
time: 4297ms
time: 4516ms
time: 4203ms
time: 4109ms
time: 4141ms
time: 4250ms
time: 4062ms

------------------------

JDK6, 50 threads, 50000 loops, -server VM:

previous:
time: 3875ms
time: 3453ms
time: 3484ms
time: 3360ms
time: 3390ms
time: 3391ms
time: 3265ms
time: 3250ms
time: 3391ms
time: 3344ms

relaxed:
time: 3235ms
time: 2921ms
time: 3000ms
time: 3016ms
time: 3094ms
time: 3062ms
time: 2782ms
time: 2640ms
time: 3016ms
time: 3000ms


------------------------

JDK 1.4.2_13, 50 threads, 50000 loops:

previous:
time: 33125ms
time: 32531ms
time: 31844ms
time: 32328ms
time: 32453ms
time: 32500ms
time: 32437ms
time: 33047ms
time: 32735ms
time: 32484ms

relaxed:
time: 34032ms
time: 32172ms
time: 32312ms
time: 27345ms
time: 32125ms
time: 31406ms
time: 31156ms
time: 31094ms
time: 32047ms
time: 31875ms

These numbers contain much more "noise" since JDK 1.4 (and JDK 1.5 as well) are much, much slower overall than JDK6; therefore the improvement is less visible. Still the results are reproducible.