Reduced performance in Java 9.0.1 (vs 8u152)

[Martin Traverso]

Hi,

We're in the process of migrating and qualifying Presto (http://prestodb.io)
to build and run on Java 9. One of the key dependencies is a library of
pure-java compression and decompression algorithms (
http://github.com/airlift/aircompressor).

In the course of trying to understand the performance characteristics when
running on Java 9, we discovered a significant drop in performance for the
compression algorithms (up to 10%) when compared to 8u152.

Here's a summary of the results and instructions on how to run the
benchmarks: https://github.com/martint/aircompressor/tree/perf

These are the outputs of JMH's perfasm profiler:

Java 8u152: https://github.com/martint/aircompressor/blob/perf/perf-8.txt
Java 9.0.1: https://github.com/martint/aircompressor/blob/perf/perf-9.txt

The generated assembly looks very different, but as far as I can tell, it's
just different decisions of when and which registers to spill.

- Martin
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