Android Garbage Collector Nursery Full

Question

I am new to android development and I am trying to understand how this Garbage Collection works but I need a clear explanation from someone first hand.

My app is doing some large transactions back and forth with a server. When I am switching from one activity to another, I constantly get the following message in my console:

GC_MINOR: (Nursery full) pause 2.77ms, total 2.95ms, bridge 11.82ms promoted 128K major 2640K los 4441K

and of course, the ms timing is different every time but it happens A LOT!

I read up on it here and created environment.txt file in my project with the following lines:

MONO_GC_PARAMS=nursery-size=1024m
MONO_GC_PARAMS=soft-heap-limit=64m

I was just testing different values at nursery-size and soft-heap-limit but it didn't help at all.

Right now, app runs REALLY slow when I go from one activity to another.
Can someone please explain in detail and present me with some options?
Thank you.

Answer 1

Garbage Collection works on different portions of heap

1. Nursery
2. Tenured

Which is different on different JVMs (Hotspot, IBM etc.) Generally Nursery size is lower than Tenured (Nursery << Tenured) Ex. In 2 GB of heap space Nusery can range from 128-512 and Remaining will be Tenured.

Nursery part will always be well managed by JVM. This part is used most of the time for new object creation, allocation as this part is lower in size GC operations (Compaction, GC collection)are fast and well tuned.

Tenured part is used when objects in Nursery grow in size or are alive for than a specific time limit (long living objects). They are maintained in Tenured. This is bigger chunk of memory and thus GC operations are slower.

Nursery pauses are generally small and shouldn't impact much when you are facing it continuously then that's sign of problem. While resizing nursery keep in mind that it should not be more than Tenured. Size is proportional to GC operations time.

In your case you should look at,

1. Existing nursery size and object allocation pattern. If objects of bigger size of getting created then try increasing nursery in multiples of 2.
2. Try parallel threads for GC operation. This can improve performance drastically.
3. Find out JVM policies ie Throughput policy, CMS policy (dependent on JVM)