RFR: 8165955: TestFullGCCount test failed with CMS and -XX:+ExplicitGCInvokesConcurrent

[Thomas Schatzl]

Hi Michail,

On Mon, 2016-11-14 at 15:52 +0300, Michail Chernov wrote:
> Hi Dima, thank you for reviewing!
> 
> Could I have a reviewer's review on this change, please?

  the change looks good.

I looked a bit through the source to see where and how the various
collectors use TraceMemoryManagerStats, and actually it seems to me the
reason that G1 can run this test with ExplicitGCInvokesConcurrent is
that unlike the other collectors it really only uses the
TraceMemoryManagerStats during a non-marking related pause, while the
others (particularly CMS) post these statistics at every STW pause.

I can imagine that this means that GC statistics for all tools that use
these do not get any relevant notifications with G1 for marking related
STW pauses (remark, cleanup).

This seems to be something that may need to be fixed. Can you file an
enhancement?

Thanks,
  Thomas