Reduced performance in Java 9.0.1 (vs 8u152)

[Martin Traverso]

Yes, I'm aware of that change. This code is allocation-free, so I wasn't expecting that to be a factor. I'll rerun the benchmarks with that and report back.

- Martin 

> On Dec 22, 2017, at 1:20 PM, Eric Caspole <eric.caspole at oracle.com> wrote:
> 
> 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
>