RFR (S): 8202842: G1 footprint regressions in jdk11+10

[Thomas Schatzl]

Hi Stefan,

On Wed, 2018-05-16 at 12:11 +0200, Stefan Johansson wrote:
> Hi Thomas,
> 
> On 2018-05-16 11:03, Thomas Schatzl wrote:
> > Hi all,
> > 
> >    can I have reviews for this change that fixes (and actually
> > improves upon the baseline) some startup footprint regression
> > introduced by changes in jdk10+10?
> > 
[...]
> > CR:
> > https://bugs.openjdk.java.net/browse/JDK-8202842
> > Webrev:
> > http://cr.openjdk.java.net/~tschatzl/8202842/webrev/
> 
> Looks good, thanks for doing the analysis and fixing this.

  thanks for your review; while talking about this change internally we
thought that it would be useful to allow the old behavior where the
FromCardCache is eagerly backed by memory.

So if AlwaysPreTouch is enabled, G1 will pretouch the G1FromCardCache
with the following change.

http://cr.openjdk.java.net/~tschatzl/8202842/webrev.0_to_1 (diff)
http://cr.openjdk.java.net/~tschatzl/8202842/webrev.1 (full)

Thanks,
  Thomas