How to identify root cause for Frequent Minor Garbage Collections using DynaTrace

Frequent young generation (minor) GCs have two root causes :

1. Small young generation size for application work load
2. High Object allocation rate

In case your old generation size is growing quickly , it is quite possible that this is linked to small young generation size. This can easily be identified using Jconsole or jstat.

In case you have high object allocation rate then it becomes difficult to identify exact root cause for the same. Performance diagnostic tools such as dynatrace provides capability to identify root cause of such issue. In order to troubleshoot high object allocation rate in dynatrace , you need to add 'RunTime Suspension' dashlet.

RunTime Suspension report a massive statistical concentration of garbage collection in any particular function. This dashlet basically provides following line of information :

1. Method Name
2. Class Name
3. Suspension Count
4. Suspension Sum[ms]
5. Suspension Avg[ms]
6. Reason

Method with high suspension count suggests that method itself allocates enough objects to fill up young generation and thus triggers a GC. This way we can find prime candidate for optimization area.