Reduced performance in Java 9.0.1 (vs 8u152)

[Eric Caspole]

Hi Martin,

As you may know, JEP 248 made G1 the default collector for 9 where it 
was ParallelGC earlier: http://openjdk.java.net/jeps/248

I tried your JMH specifying +UseParallelGC by JMH annotations and the 
performance of 9 seems quite even to 8u131 that I have handy.

Maybe you could try this for yourself and see how it goes.

Regards,
Eric

On 12/22/2017 12:59 PM, Martin Traverso wrote:
> 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