Frequent out of memory issues - out-of-memory

Question

We are running web application with 6GB heap assigned to it. But, after some time, it is giving out of memory.
The exception stack trace is given below.
Exception in thread "com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2" java.lang.OutOfMemoryError: PermGen space
00:46:52,678 WARN ThreadPoolAsynchronousRunner:608 - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector#772df14c -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
00:46:52,682 WARN ThreadPoolAsynchronousRunner:624 - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector#772df14c -- APPARENT DEADLOCK!!! Complete Status:
Managed Threads: 3
Active Threads: 0
Active Tasks:
Pending Tasks:
com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask#3e3e8a19
Pool thread stack traces:
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,]
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,]
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,]
Exception in thread "Task-Thread-for-com.mchange.v2.async.ThreadPerTaskAsynchronousRunner#6bbc0209" java.lang.OutOfMemoryError: PermGen space
Exception in thread "com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1" java.lang.OutOfMemoryError: PermGen space
Exception in thread "com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0" java.lang.OutOfMemoryError: PermGen space
Exception in thread "com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2" java.lang.OutOfMemoryError: PermGen space
Is this the problem with C3p0 Connection pool?

Answer 1

According to the last few messages, you could be running out of PermGen memory. According to your post, the 6 GB are assigned to heap. If you have enough physical memory, double the memory assigned to PermGen. If the problem persists (and happens after more or less the same amount of time), revert the changes and consider analyzing heap through appropriate methods.
Use
-XX:PermSize=1024m -XX:MaxPermSize=1024m
for a 1-GB (1024 MB) allocation. You could need more.

Answer 2

Rather than guessing, my advice is to use a memory profiler to examine the contents of the heap when you run out of memory. This will give you a definitive answer as to what's taking all the memory, and would let you make informed choices as to what steps to take next.

Answer 3

You are getting permgen out of memory. This is more difficult to resolve than normal out of memory. Its not linked to usage of C3p0.
You need to do memory profiling and see whats taking up permgen space.
As a temporary measure , you can increase permgen space by using -XX:PermSize -XX:MaxPermSize
If you are using spring then one of common reasons for this error is improper usage of cglib library.

Answer 4

c3p0 and Tomcat's somewhat unusual and difficult implementation of class(un)loading under hot redeploy can lead to permgen memory issues. the next c3p0 pre-release has some fixes for this problem; they are implemented already, but for now you'd have to build from source via github, which is not necessarily easy.
in c3p0-0.9.5-pre4 and beyond, setting config param privilegeSpawnedThreads to true and contextClassLoaderSource to library should resolve the issue. i hope to release c3p0-0.9.5-pre4 within the next few days.