[RHEL5] Many processes changed to uninterruptible state and system hanged.

Issue

• Our customer encountered a problem that cluster software performed shutdown due to detection of a server hang(high load).
• We found that kswapd and rysnc changed to uninterruptible state a little before hang-up and that load average went up at the same time. We guess that this problem corresponds to following BZ, but it is not cirtain yet.
• Bug 609668 - kswapd hung in D state with fragmented memory and large order allocations

https://bugzilla.redhat.com/show_bug.cgi?id=609668