Comment 17 for bug 151168

Although I'm obviously biased (as the one who wrote ring), I have to say that I really, really doubt there is a leak that may fill several hundred megabytes of memory inside ring.
Besides the usual boilerplate code that every compiz plugin has, there is only one place of allocation where a 8 byte structure is allocated for each window in the ring. So even if it wasn't freed correctly (which it is here), it would take ages to fill up memory with that allocation, unless you have a really absurd amount of windows in the ring.
The second place where stuff is allocated from ring is the window title display (which is also freed just fine here) ... if you want to check that, just disable either the window title display or the text plugin.

For me, the issue sounds like a driver problem, just as sampsa wrote before me.