All my JVM does is full GC's

Question

I have a simple application, it doesn't use much memory.
In the beginning, as the heap expands, I get my incremental GCs.
But eventually, I get Full GCs, and after that all I get is full GCs. No matter how much memory I give my app.
My app doesn't require a lot of memory. After GC it rarely goes above 8M.
I've run it with everything from -Xmx16m up to -Xmx64m.
When I PrintGCDetails, or look at it through jconsole, the tenured generation is always full.
$ java -version
java version "1.5.0_11"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_11-b03)
Java HotSpot(TM) Client VM (build 1.5.0_11-b03, mixed mode)
java -Xmn16m -Xmx16m -verbose:gc -XX:+PrintGCDetails
[Full GC [Tenured: 2047K->2047K(2048K), 0.1542593 secs] 16831K->5629K(16832K), [Perm : 24339K->24339K(24576K)], 0.1543772 secs]
If I run with 64M, it just takes longer before the Full GC, but I never get the incrementals again, and the Tenured space is still 2MB.
java -Xmn16m -Xmx16m -verbose:gc -XX:+PrintGCDetails
[Full GC [Tenured: 2047K->2047K(2048K), 0.2037613 secs] 61055K->7943K(61056K), [Perm : 27706K->27
706K(27904K)], 0.2038618 secs]
I'm assuming I'm getting the Full GCs because the Tenured generation is full. But I can't seem to find a way to change the size. I tried NewRatio, but it didn't seem to have any affect at all.
This isn't really a performance issue, but it is a pedantic issue as I don't think I should be doing Full GCs all of the time, that just seems like an "unhealthy" or at least "out of balance" JVM/Application configuration, so I'd like to get the GC working better in a healthier way with more incremental GCs rather than always doing Full GCs.
Any hints would be appreciated.

Answer 1

Why Xmn == Xmx? (Maybe just for experimental test....)
As gc log says, your tenrued size is always only < 2M size. Why? because you set new generatio size == max heap size. JVM set the tenured size to its minimum.
Tenured size is so small that your young objects located in new space cannot be promoted to tenured space. So JVM decides to start full gc - to clear all the garbages.
For this reason, it is unresonable and meaningless to set young generation size > tenured generation size. It might cause full gc continuously.
Additionaly, keep in mind that too big young generation sometimes has tendency to make problems related to full gc.