RFR (S): 8154528: Reclaim regions emptied by marking in Remark pause

Stefan Johansson stefan.johansson at oracle.com
Tue Apr 3 12:53:44 UTC 2018

Thanks for yet another nice improvement of G1 Thomas,

On 2018-03-29 16:49, Thomas Schatzl wrote:
> Hi all,
>    can I have reviews for this change that moves the space reclamation
> of empty regions into the Remark pause, which makes these regions
> available much sooner than before, with the obvious benefits of doing
> so.
> The Cleanup pause now only contains updating the remembered set states
> after rebuilding remembered sets and determining the collection set
> candidates. In the future we might be able to make those concurrent and
> drop the Cleanup pause completely.
> There is not much too say here, after all the recent refactorings this
> patch is almost trivial :)
>  From a timing POV this adds a few ms to the Remark pause in my
> measurements, mostly from the code root purging moved here. I think
> there is enough opportunity in the remark pause to decrease its
> duration in the future that outweighs the mentioned benefits.
> Thanks go to everyone reviewing so far, particularly StefanJ and
> Sangheon!
> Depends on JDK-8178105.
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8154528
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8154528/webrev/

The change looks good, but I realized that reclaim_empty_regions() uses 
a task named G1CleanupTask. This naming is a bit unfortunate now since 
this is not the cleanup phase anymore, but still correct since we are 
doing cleanup. What do you think about renaming it to G1CleanRegionTask 
or G1ReclaimRegionTask? I also see that "cleanup" ripples down a bit but 
I don't think we need to change that. I'm fine with not doing anything 
at all but if you dislike the suggestion, but I wanted to raise the 


> Testing:
> hs-tier 1-5
> Thanks,
>    Thomas

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