Menu
I'm wondering what are the exact situations that trigger Full Garbage Collection in Java.
The obvious ones are:
What about other cases that cause full gc? Particularly:
I'm running Sun Java 1.6 and using Concurrent Mark-Sweep and ParNew for new gen.
587
A Full GC will be triggered whenever the heap fills up. In such a case the young generation is collected first followed by the old generation.
The root cause of high-frequency garbage collection is object churn—many objects being created and disposed of in short order. Nearly all garbage collection strategies are well suited for such a scenario; they do their job well and are fast. However, this still consumes resources.
Garbage collection in Java is the process by which Java programs perform automatic memory management. Java programs compile to bytecode that can be run on a Java Virtual Machine, or JVM for short. When Java programs run on the JVM, objects are created on the heap, which is a portion of memory dedicated to the program.
As long as an object is being referenced, the JVM considers it alive. Once an object is no longer referenced and therefore is not reachable by the application code, the garbage collector removes it and reclaims the unused memory.
I've observed one more situation that triggers a full GC in Java Hotspot VM 1.6 64bit on Ubuntu, using Concurrent Mark-Sweep:
If -XX:PermSize value does not equal to -XX:MaxPermSize (e.g. is smaller), an occasional Full GC happens when java needs to expand the PermGen (even though it does not need to allocate more memory than MaxPermSize). So setting -XX:PermSize and -XX:MaxPermSize to be the same seems like a good idea.
136
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
