Question

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Java garbage collector – When does it collect?

When people say that garbage collector in Java is slowing the whole application down, what do they really mean by it? Isn’t garbage collector only gets triggered whenever an Object is relieved? Please help me understand. Thank’s!

Answer 1

Take a look at http://developers.sun.com/mobility/midp/articles/garbage/

As Java technology becomes more and more pervasive in the telecommunications (telco) industry, understanding the behavior of the garbage collector becomes more important. Typically, telco applications are near-real-time applications. Delays measured in milliseconds are not usually a problem, but delays of hundreds of milliseconds, let alone seconds, can spell trouble for applications of this kind. Quite simply, sub-optimal performance translates directly into loss of revenue.

Basically, if the garbage collector compacts a small heap then the delay is short, but if you have been generating a lot of garbage, and have a large reachable object graph, you can see large delays. New garbage collection algorithms (generational / incremental GC) have mitigated this to some degree but tuning GC is still somewhat a black art.