compaction on Nursery Collection

Bernd Eckenfels bernd-2012 at eckenfels.net
Tue Dec 11 16:33:38 PST 2012


> On Dec 9, 2012, at 12:58 PM, Xin Tong <xerox.time.tech at gmail.com> wrote:
>
>> I am wondering why compaction is only run on full collection. but not
>> Nursery Collection in parallel throughput GC in hotspot ?

The ParNewGC is a copying collector which does compaction by definition  
(since it only copies surviving objects).

What is collected and how depends on the GC strategies used - for each  
generation and GC type differently.

Maybe you want to describe your problem more fully. I dont think you see  
fragmentation in Nursery ever (you might see other problems like arge  
allocations, TLA sizing or similiar which does feel like fragmentation  
problems but effectively is not).

Let us know what command line switches you have used and what VM Version  
you run (and actually I think that part of the question is better done on  
-user mailinglist).

Gruss
Bernd
-- 
http://bernd.eckenfels.net


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