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

[Thomas Schatzl]

Hi,

On Tue, 2019-07-23 at 14:15 -0700, sangheon.kim at oracle.com wrote:
> Hi Thomas,
> 
> On 7/22/19 1:41 AM, Thomas Schatzl wrote:
> > Hi Kim,
> > 
> > On Sat, 2019-07-20 at 22:03 -0400, Kim Barrett wrote:
> > > > On Jul 19, 2019, at 6:42 PM, Kim Barrett <
> > > > kim.barrett at oracle.com>
> > > > wrote:
> > > > 
[...]
> > > Oops, I realized later that I missed something.
> > > 
> > > ---------------------------------------------------------------
> > > ----
> > > -----------
> > > src/hotspot/share/gc/g1/g1DirtyCardQueue.hpp
> > >   156     return align_up(num_entries_in_completed_buffers(),
> > > buffer_size()) / buffer_size();
> > > 
> > > align_up requires the alignment value to be a power of 2, but the
> > > buffer size is not required to be a power of 2, so this doesn't
> > > work. It just so happens that the default buffer_size *is* a
> > > power of 2 (G1UpdateBufferSize defaults to 256), and we probably
> > > don't have any tests that use a non-default buffer_size.
> > > 
> > > 
> > 
> > Oops.
> > 
> > http://cr.openjdk.java.net/~tschatzl/8227719/webrev.1_to_2 (diff)
> > http://cr.openjdk.java.net/~tschatzl/8227719/webrev.2 (full)
> 
> webrev.2 looks good.
> 
> Thanks,
> Sangheon

thanks for your review.

Thomas