examples of garbage collection bottlenecks

Question

I remembered someone telling me one good one. But i cannot remember it. I spent the last 20mins with google trying to learn more.

What are examples of bad/not great code that causes a performance hit due to garbage collection ?

Answer 1

When you have some loop involving the creation of new object's instances: if the number of cycles is very high you procuce a lot of trash causing the Garbage Collector to run more frequently and so decreasing performance.

Answer 2

• frequent memory allocations
• lack of memory reusing (when dealing with large memory chunks)
• keeping objects longer than needed (keeping references on obsolete objects)

Answer 3

I can give you an example that will work with the .Net CLR GC:

If you override a finalize method from a class and do not call the super class Finalize method such as

protected override void Finalize(){
    Console.WriteLine("Im done");
    //base.Finalize(); => you should call him!!!!!
}

When you resurrect an object by accident

protected override void Finalize(){
    Application.ObjJolder = this;
}

class Application{
    static public object ObjHolder;
}

When you use an object that uses Finalize it takes two GC collections to get rid of the data, and in any of the above codes you won't delete it.

Answer 4

In most modern collectors, any use of finalization will slow the collector down. And not just for the objects that have finalizers.