strange OutOfMemory when creating big trove collection

Question

In my app start up, I'm creating trove long hash set with 75*10^6 capacity.

Profiler shows, that app use 1.4g for it. I'm try to set -Xmx1600m, and catch out of memory.

-Xmx2000m same.

-Xmx2030m same.

-Xmx2040m OK.

Profiler doesn't see so big allocation, where and why it's happen?

Answer 1

Most likely your tenured space is not large enough. The jvm might not be smart enough to shrink other regions to allow you such a large continuous block. Note CMS doesn't defrag so you can get this problem with much smaller arrays.

For a collection that big you might consider using off heap memory.