JEP 173: Remove Rarely-Used Combinations of Garbage Collectors

Bengt Rutisson bengt.rutisson at
Thu Dec 6 13:32:32 UTC 2012

Hi Peter,

Thanks for your feedback!

On 12/6/12 1:23 AM, Peter B. Kessler wrote:
> mark.reinhold at wrote:
>> Posted:
>> - Mark
> If the only use of SerialOld will be with ParallelScavenge + 
> SerialOld, then maybe we should check what the performance hit (GC 
> time, heap utilization, application throughput) is using 
> ParallelScavenge + ParallelOld, possibly with ParallelOld throttled 
> down to 1 worker thread.  (I understand that we can't remove the code 
> for SerialOld because it backs CMS, but we could improve the user 
> experience by not letting people choose sub-optimal configurations.)  
> Similarly, if we could start weaning users off of DefNew we might 
> eventually be able to remove the code for it.

These are very good observations. In fact I look at the currently 
proposed JEP as a first step in a direction towards much fewer GC 
combinations. I think what you suggest is a good path forward, but there 
may be other step we want to take as well.

> It would help the write-up if the *supported* configurations were listed.

Good point. I'll try to write that up and add it to the JEP.


>             ... peter

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