[12] RFR (XS): 8215548: G1PeriodicGCSystemLoadThreshold needs to be a double

[Thomas Schatzl]

Hi all,

  can I have reviews for this small change that changes the
G1PeriodicGCSystemLoadThreshold value type from an uintx to a double?

(Manual) Testing by Ruslan from jElastic showed that integers are too
coarse for this value, as typical load values you want to compare with
are ~0.5.

Unfortunately this has not been discovered during review; also testing
against a particular load value provided by the OS is hard, so there
has not been a regression test for this particular flag where this
probably would have been found out. :(

CR:
https://bugs.openjdk.java.net/browse/JDK-8215548
Webrev:
http://cr.openjdk.java.net/~tschatzl/8215548/webrev/
Testing:
Manual testing with a hacked gc/g1/TestPeriodicCollection.java test,
and the command line range checking tests.
hs-tier1-5

Thanks,
  Thomas