RFR: JDK-8224963: Char-Byte Performance Enhancement

[Adam Farley8]

Hi Vladimir,

I have a locally-written performance test I used to get the "6x". 
Will chase up with the guy who wrote it to see if I can share it. 
If not, I'll write a new one.

As for the enhancements, two options are:

- matching on the new method names, and replacing the inner logic 
with some souped-up version of said logic. 

- alter the code to match on one of the C2 idioms, though I imagine 
if it were that simple, OpenJDK would come with a list of said 
idioms so everything people write can be easily accelerated by the 
JIT.

As for how OpenJ9 does it specifically, I don't know, and I suspect 
it's safer if I don't find out, contamination-wise.

Does any of that help?

Best Regards

Adam Farley 
IBM Runtimes


Vladimir Ivanov <vladimir.x.ivanov at oracle.com> wrote on 29/05/2019 
13:22:27:

> From: Vladimir Ivanov <vladimir.x.ivanov at oracle.com>
> To: Adam Farley8 <adam.farley at uk.ibm.com>, hotspot-compiler-
> dev at openjdk.java.net
> Date: 29/05/2019 13:22
> Subject: Re: RFR: JDK-8224963: Char-Byte Performance Enhancement
> 
> 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://urldefense.proofpoint.com/v2/url?
> u=https-3A__bugs.openjdk.java.net_browse_JDK-2D8224963&d=DwIC-
> g&c=jf_iaSHvJObTbx-siA1ZOg&r=P5m8KWUXJf-
> CeVJc0hDGD9AQ2LkcXDC0PMV9ntVw5Ho&m=4XPqGhxLchCLvSQhTIu3Wvm63NE2XpuEJf-
> PzjFCXb4&s=2ChxP3IE0tkvevxSXfil3PGlpEHkUPxgwMxHH5J-A34&e=
> > 
> > Example Webrev: _https://urldefense.proofpoint.com/v2/url?
> u=http-3A__cr.openjdk.java.net_-7Eafarley_8224963_webrev_-5F&d=DwIC-
> g&c=jf_iaSHvJObTbx-siA1ZOg&r=P5m8KWUXJf-
> CeVJc0hDGD9AQ2LkcXDC0PMV9ntVw5Ho&m=4XPqGhxLchCLvSQhTIu3Wvm63NE2XpuEJf-
> PzjFCXb4&s=fCeNvvk3Fehc6ssZfoNkJao_NJyoxeov7cxiyMSvuwQ&e=
> > 
> > Best Regards
> > 
> > Adam Farley
> > IBM Runtimes
> > 
> > Unless stated otherwise above:
> > IBM United Kingdom Limited - Registered in England and Wales with 
number 
> > 741598.
> > Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 
3AU
> 

Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number 
741598. 
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
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