Now I have a very serious performance problem with the way (the "X/Y" way) I compose the string id when using Pojo cache. I have one PojoCache instance globally shared by 20 threads in websphere, but those 20 threads are mostly in the "waiting" state by what I see with JProfiler, the hotspots are: - 6.2% - 30,415 s - 9,479 hot spot inv. org.jboss.cache.util.concurrent.locks.OwnableReentrantLock.tryLock - 2.0% - 10,057 s - 5,065 hot spot inv. org.jboss.cache.mvcc.MVCCNodeHelper.acquireLock (line: 259) While the threads are waiting, the CPU usage is nearly zero (there are some daemon threads running periodically in websphere). It is not a real deadlock because all processing eventually finished without. What I don't understand is that why in majority of the time those threads are waiting for each other but no one is really busy? No matter how I compose the key, I would expect at least one thread is busy at a certain moment. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4244944#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...