EA612: Full Garbage collection at each minor collection

Questions about YourKit Java Profiler
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mschulz
Posts: 17
Joined: Mon May 16, 2005 8:40 pm

EA612: Full Garbage collection at each minor collection

Post by mschulz »

When I run the application instrumented with yjp, a Full GC cycle
occurs just after each minor collection.

Is yjp doing this purposefully?

Why? Trying to reduce the memory footprint of any snapshots?

Thanks!
Martin
Anton Katilin
Posts: 6172
Joined: Wed Aug 11, 2004 8:37 am

Post by Anton Katilin »

The profiler agent does not do any explicit GCs, unless user manually presses corresponding link in the Control Panel. There were explicit GCs in previoues versions, but not in this EAP.

How did you find that?
mschulz
Posts: 17
Joined: Mon May 16, 2005 8:40 pm

Post by mschulz »

-verbose:gc -XX:+PrintGCDetails

I've set the main heap to 3GB and am still getting the Full GC cycles
way too frequently - however under load they only occur every third
GC of the young generation.

The pattern is quite different and as expected when I start the appserver without yjp.
Anton Katilin
Posts: 6172
Joined: Wed Aug 11, 2004 8:37 am

Post by Anton Katilin »

Hi,

Very interesting.
What is the exact version of JVM? (e.g. what java -version prints)

We'll consult SUN engineers regarding this issue.
mschulz
Posts: 17
Joined: Mon May 16, 2005 8:40 pm

Post by mschulz »

1.5.0_03 - Sparc 64-bit installed - running 32 bit.

The interval appears to be exactly 60s (plus the GC time),
and there's always a minor colletion followed by a full collection.

Under more load, additional minor collection are occurring.

From telemetry point of view, this is fairly convenient, as I
can look at the old generation and get to see the current state
at fixed measurement intervals.

It would be good to make such a feasure optional though.
Anton Katilin
Posts: 6172
Joined: Wed Aug 11, 2004 8:37 am

Post by Anton Katilin »

I'm sorry, I don't understand which feature you mean.
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