RFR (L): 8073013: Add detailed information about PLAB memory usage

Thomas Schatzl thomas.schatzl at oracle.com
Thu Aug 6 16:01:19 UTC 2015

Hi all,

  just one minor addition: this change is based on all recent RFRs
including 8003237 (the evacuation failure speedup change) and 8133042
(remove some friends in g1collectedheap).

For the others a push job is on its way.


On Thu, 2015-08-06 at 17:49 +0200, Thomas Schatzl wrote:
> Hi all,
>   can I have reviews for this change that prepares for a lot of changes
> related to 8030849 "Investigate high fragmentation/waste in some
> situations during allocation during GC in G1"?
> Before investigating and fixing fragmentation during PLAB, we need to
> track that information.
> For this reason, PLABStats has been extended in a G1EvacStats class with
> the necessary information that is needed to do better PLAB sizing, in
> particular G1EvacStats::_region_end_waste that tracks the waste at the
> end of regions during refill, G1EvacStats::_regions_filled that tracks
> the number of region refills, G1EvacStats::_inline_allocated that tracks
> the amount of inline allocation (excluding PLAB allocation),
> G1EvacStats::_failure_used and G1EvacStats::_failure_waste that track
> memory usage in regions where evacuation failure occurred.
> There had to be somewhat extensive changes particularly to get the
> _region_end_waste in the allocation classes, which is what makes this
> change a bit large.
> Overall there is no change in the sizing policy except for accounting
> _region_end_waste.
> As you may notice, there is a new JFR event, but no real additional
> logging for the log file (the -XX:+PrintPLAB message has been extended
> though). That will be added in an extra CR, as soon as the new logging
> framework has been added.
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8073013
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8073013/webrev
> Testing:
> jprt, a few aurora runs, local testing, lots of benchmarks mainly in
> conjunction with the following changes.
> Thanks,
>   Thomas

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