If a file or directory in /proc is kept open after a task has exited, its inode retains a reference to the task struct, thus preventing a large chunk of memory from being freed. Under the right workload, staggering amounts of ram can be eaten by dead task structs that are being pinned by /proc inodes.

Version-Release number of selected component (if applicable):
2.6.9-89.0.11

Additional info:

Patch to address this issue is:
99f895518368252ba862cc15ce4eb98ebbe1bec6

With a followup:
13b41b09491e5d75e8027dca1ee78f5e073bc4c0