Request for review - 8022817: CMS should not shrink if compaction was not done

Jon Masamitsu jon.masamitsu at oracle.com
Wed Aug 14 19:49:22 PDT 2013


Ramki,

Thanks for the review.


On 8/14/2013 1:37 AM, Srinivas Ramakrishna wrote:
> Looks OK to me.
>
> Aside: Is all of that code for ASConcurrentMarkSweepGeneration planned
> to be used, or is it best to get rid of all the dead code?

It depends :-).  If we implement a throughput mode in G1 and decide
to reimplement the throughtpu GC ergonomics, then we will remove this code.
The code such as in ASConcurrentMarkSweepGeneration is the
GC ergonomics implemented in the G1 style (shared with CMS)
and would be reusable in the a G1 throughput mode with the same
(or derivative) GC ergonomics.  My opinion.

Jon

>
> -- ramki
>
> On Mon, Aug 12, 2013 at 12:09 PM, Jon Masamitsu
> <jon.masamitsu at oracle.com> wrote:
>> 8022817: CMS should not shrink if compaction was not done
>>
>> If UseCMSCompactAtFullCollection is turned off, a full GC that is done in
>> the foreground but does
>> not compact should not shrink the generation. In that case  a mark-sweep was
>> done so the free space
>> is maintained in freelists (not as a contiguous area at the end of the
>> generation) and shrinking for
>> freelists is not implemented.
>>
>> http://cr.openjdk.java.net/~jmasa/8022817/webrev.00/
>>
>> Thanks.
>>
>> Jon



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