java – AnonPage memory leak

Our service notices some hosts having large anon pages like these from pmap -x:

0000000580000000 9486088 9479172 9479172 rw— [ anon ]

meanwhile, our other regular hosts have much smaller anon pages like

0000000580000000 9486176 5730788 5730788 rw— [ anon ]

What possibly creates such large blocks?

I’ve tried heap dumping the process but the resulting heaps are about the same size. The difference in AnonPages account for ~3 gigs of extra memory the process uses.