RFR (S): 8227719: G1 pending cards estimation too conservative for cost prediction

[Thomas Schatzl]

Hi Kim,

  thanks for your thoughts on this.

On Thu, 2019-07-18 at 19:05 -0400, Kim Barrett wrote:
> > On Jul 18, 2019, at 4:33 PM, Thomas Schatzl <
> > thomas.schatzl at oracle.com> wrote:
> > 
> > [...]
> 
> I suggested keeping completed_buffers_num() for now, using a
> definition of ceiling(card_count / buffer_size()), to reduce the
> fanout of the change to internally carry around card counts rather
> than buffer counts.  I can deal with followup on that as part of
> working on improving DCQS and refinement thread control, which I
> think I'm finally ready to start working on again, now that my
> PtrQueue[Set] refactoring work seems to be approaching completion.
> 
>
> I would prefer to only be managing one counter rather than two,
> especially as I start looking at mitigations for the DCQS lock.
> 

New webrev at

http://cr.openjdk.java.net/~tschatzl/8227719/webrev.0_to_1 (diff)
http://cr.openjdk.java.net/~tschatzl/8227719/webrev.1 (full)

which removes the buffer count, and replaces the
"completed_buffers_num" method with what you suggested.

I did some very cursory perf testing with no differences.

Thanks,
  Thomas