RFR (XS): 8200723: Suppress rs_length and predicted_cards sampling during mixed gcs

[Thomas Schatzl]

Hi Kim, Stefan,

On Mon, 2018-04-16 at 22:35 -0400, Kim Barrett wrote:
> > On Apr 4, 2018, at 6:35 AM, Thomas Schatzl <thomas.schatzl at oracle.c
> > om> wrote:
> > 
> > Hi all,
> > 
> >  can I have reviews for this small change that fixes a throughput
> > problem G1 may show after mixed gc phase?
> > 
> > 
> > [...]
> > CR:
> > https://bugs.openjdk.java.net/browse/JDK-8200723
> > Webrev:
> > http://cr.openjdk.java.net/~tschatzl/8200723/webrev
> > Testing:
> > hs-tier 1-5 with many other changes over time; manual inspection of
> > eden sizing behavior of several known to be affected benchmarks
> > 
> > Thanks,
> >  Thomas
> 
> I was going to question whether there might be a problem with the
> call to update_rs_lengths_prediction at line 711, which will might be
> using stale data.  Except it doesn't update except for young-only
> collections.
> 
> Why do the calls to report_pending_cards and report_rs_lengths at
> lines 694-5 cast the arguments to double?  I really dislike casts...
> 

Yeah, some code that would need a lot of refactoring...

> Change looks good.
> 

  thanks for your reviews.

Thomas