Non-terminating Java process?

Question

Hi,
I have a very memory intensive Java process. The heap grows to somewhere between 1GB and 1.2GB. Basically, when I use the -Xmx1000M option I get the java.lang.OutOfMemory Error but when I use -Xmx1200M then it runs to completion.
When I use the option -Xmx1100M then my program doesn't give me the out of memory error but it also never finishes. I am wondering if there is some weird state that it is sitting in, like maybe there is just enough memory to load the garbage collector, but not enough to have it do anything.
See, when I give my process the -Xmx1200M option it runs in a few hours, less than 2 hours for sure. But with the -Xmx1100M option it will stay alive for 12 hours or more but never finish.
Any comments appreciated.
Thanks.

Answer 1

When the heap limit is met, a full gc is run. Ifthat
doesn't free enough memory, then anOutOfMemoryError
is thrown.
As for the extremely long runtime given -Xmx1100M,
I'm thinking it's sort of pinging off its ceiling,so
to speak, and running full gc's very often.Thank you. That is the type of answer I was hoping
to get.
So from what you said and the fact that my program
fails at 1GB of heap but suceeds at 1.2 GB, I infer
the following: the heap size that my program requires
is around 1100 MB. When it gets close to that,
garbage collection will run but will only free enough
to do "a little bit" of work, like create the next
few objects, then GC needs to run again, etc.
Basically, hardly any memory is getting freed by GC,
, but just enough is so my program can run a tiny bit
before GC is required to run again.
Does that sound about right?That works.