Reduced performance in Java 9.0.1 (vs 8u152)

[Dawid Weiss]

> do with a different unrolling strategy which perhaps leads to more
> spilling.  8u152 has a tighter inner loop. It's just one of those
> things which happens sometimes with JIT compilers, IMO.  G1 is a red
> herring.

I don't have enough knowledge of JIT internals to argue, but my
experience and real-life software
runs clearly show the difference Martin mentioned within a single JVM version.

JDK, GC, Time
8, g1, 3h 25m
8, par (default), 3h 0m

Again -- this is a particular result, but they're very repeatable and
the average/ variance is definitely
not accidental.

Dawid