RFR: JDK-8224963: Char-Byte Performance Enhancement

Vladimir Ivanov vladimir.x.ivanov at oracle.com
Wed May 29 12:22:27 UTC 2019

Hi Adam,

The bug mentions ~6x improvement in throughput. Are there have any 
microbenchmarks you can share which demonstrate that? That would greatly 
simplify the analysis of changes you propose.

Also, if you can elaborate on what optimization opportunities C2 misses 
in original code, please, do.

Best regards,
Vladimir Ivanov

On 29/05/2019 12:45, Adam Farley8 wrote:
> Hi All,
> Could someone familiar with the Hotspot JIT please review and opine on 
> the below?
> The Char-Byte encoding/decoding methods inside some of the sun.nio.cs 
> classes
> (such as US_ASCII) see a lot of use, and OpenJDK on the OpenJ9 VM seems to
> do this a lot faster.
> Is it possible to achieve a similar improvement on OpenJDK on Hotspot by
> tweaking the CL code to match Hotspot JIT compiler idioms, or by 
> introducing
> a method name for the HS JIT to match on?
> An example of these changes to US_ASCII.java is linked below. No OpenJ9 
> code
> is included in the work item or the webrev, to avoid contamination.
> Work item: https://bugs.openjdk.java.net/browse/JDK-8224963
> Example Webrev: _http://cr.openjdk.java.net/~afarley/8224963/webrev/_
> Best Regards
> Adam Farley
> IBM Runtimes
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> 741598.
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