I just encountered a problem during a FCS run where the client would pause every few seconds. Looking at the heap usage stats, it looks like Eden and Tenure space are literally full 100% of the time, and isn't getting cleaned up during GC operations.. The result is survivor space constantly filling up and triggering a full CG to clear it out, and appears to continue for the life span of the VM.
Submitted a bug report to snapshot to whatever it can capture, and kept a copy of the heapdump in case it might be useful.
System:
Intel i7 860
8GB Ram
Win7 Pro 64-bit
Video: NV GTX 590
JVM: Oracle JRE 7 - 7.0.0.147
Steam enabled
My friend was having a memory leak issue.
He'd play fine for a while, but the game started getting worse and worse, and eventually crashed for being "out of memory".