[jboss-user] [JBossCache] - Reading threads are blocked

We are currently testing the 2.0 CR2 in a load intensive environment. I started to notice a lot of blocked threads that were blocked by the cache. In order to investigate further I constructed a simple load test on a cache. The cache uses the standard replAsync-service.xml This is what I do: 1. Create a cache | 2. Initialize the cache with some nodes and data | 3. Start a large number of concurrent readers | 4. Observe the threads and monitors in the system using jprofiler | | | Contents of the created and initialized cache: | | | DEBUG CacheLockGetTest - null {} | | /d {} | | /g {1=Data} | | /h {1=Data} | | /f {1=Data} | | /e {1=Data} | | /b {} | | /g {1=Data} | | /h {1=Data} | | /f {1=Data} | | /e {1=Data} | | /a {} | | /g {1=Data} | | /h {1=Data} | | /f {1=Data} | | /e {1=Data} | | /c {} | | /g {1=Data} | | /h {1=Data} | | /f {1=Data} | | /e {1=Data} | | | | The task used to read from the cache: | | | | private class CacheExecutor implements Runnable { | | private final Fqn fqn; | | public CacheExecutor(Fqn fqn) { this.fqn = fqn; } | | | | public void run() { | | cache.get(fqn, 1); | | } | | } | | | | | The cache has been initialized before I start the readers, so that when the readers are running no write occurs on the cache. Now, I thought that read operations on the cache would be concurrent but when inspecting the threads in jprofiler I got this: | | http://www.robotsociety.com/cache/threads.GIF | | If we look at the contending threads' stack traces we see that they all block against UnversionedNode (See: http://www.robotsociety.com/cache/monitors.GIF) | | I have looked at unversioned node and there is much synchronization going on in there. I am not sure why the blocking is so frequent and I also saw threads working in different regions blocking each other. | | One question is, if I access a/b/c, will a read lock be acquired for all those nodes, if so then we will ultimately have synchronization on the common root node for all read operations in the cache, correct? | | I understand that the test above is a bit artificial since we do not run any other type of logic that would permit pauses for access, but I also run into this blocking issues in our server where we do execute other functionality. | | Now, our cache is pretty large so I will try and divide the regions into separate caches to minimize the synchronization issues or try to find some other workaround, but shouldn't a cache solution permit more concurrent access rather then having what looks like a global sync lock? | | On a side note, after running a while the UnversionedNode sync lock is replaced by the readOwnerList_ in LockMap (see: http://www.robotsociety.com/cache/monitors_copyarray.GIF). View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4053977#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...