Re: A few micro-benchmarks for Jython 2 and two other ideas

On 06/01/2021 02:33, Thad Guidry wrote:
> Hi Jeff!
>
> I'm from the OpenRefine team where we are constantly watching the 
> future of Jython since we use it as an expression language within 
> OpenRefine, along with Clojure.
> We've talked on the mailing list I think in the past, perhaps not.
>
I think we have. Thanks for your continued interest in Jython.

> Regarding the microbenchmarks and your analysis...and some of the 
> anomalies you found...
> I'm wondering if you verified that SIMD, SSE, etc. intrinsics were 
> being used or not sometimes?
> https://www.amd.com/system/files/TechDocs/25112.PDF#G14.232935 
> <https://www.amd.com/system/files/TechDocs/25112.PDF#G14.232935>
>
Yes, I found similar information: that's what led to my conclusions 
about the quartic test. I'm impressed HotSpot is able to use them.

> And to see if intrinsic methods are being utilized or not and where in 
> compiled code, you can add:
>     -XX:+PrintCompilation -XX:+UnlockDiagnosticVMOptions 
> -XX:+PrintInlining
>
Unlock has to come first, it seems. I've experimented with those options 
and found what they produced was pretty incomprehensible. I never made 
the disassembly option work.

Going back and trying a little harder, thanks to your suggestion, I got 
further this morning. The output remains too complex for me to follow 
(so many jumps!), but a superficial inspection supports the conjectures 
I made based only on timing. In particular, of the three fixtures, only 
for Jython 2 does the JVM manage to in-line the floating point 
arithmetic into quartic(). It contains this in what I assume is the fast 
path:

   0x00000202187735df: movapd  xmm3,xmm0
   0x00000202187735e3: addsd   xmm3,xmm2
   0x00000202187735e7: subsd   xmm2,xmm0         ;*dsub {reexecute=0 
rethrow=0 return_oop=0}
                                                 ; - 
org.python.core.PyFloat::float___sub__@23 (line 486)
                                                 ; - 
org.python.core.PyFloat::__sub__@2 (line 477)
                                                 ; - 
org.python.core.PyObject::_basic_sub@2 (line 2192)
                                                 ; - 
org.python.core.PyObject::_sub@31 (line 2177)
                                                 ; - 
uk.co.farowl.jy2bm.PyFloatBinary::quartic@33 (line 86)
   0x00000202187735eb: mulsd   xmm3,xmm1

I added a task to the Gradle scripts that dumps the compiled code (if 
one has the hsdis-amd64 plug-in) as I'm sure to forget how I did this.

https://github.com/jeff5/very-slow-jython/blob/333f61d54787f7499ec8141eafe6b8c5c04f0cea/jy2bm/jy2bm.gradle#L74

> You might also be thought provoked with some extra information within 
> this JEP:
> https://bugs.openjdk.java.net/browse/JDK-8205637 
> <https://bugs.openjdk.java.net/browse/JDK-8205637>
>
> Some Java JVM compilers & many of Java's robust libraries completely 
> miss the point of sometimes using Intrinsic functions as often as 
> possible. For example: SSE 4.2 
> https://software.intel.com/sites/landingpage/IntrinsicsGuide/#expand=898,2862,2861,2860,2863,2864,2865&techs=SSE4_2 
> <https://software.intel.com/sites/landingpage/IntrinsicsGuide/#expand=898,2862,2861,2860,2863,2864,2865&techs=SSE4_2>and 
> the reason why Azul's Zing JVM is fast, is because it DOES use 
> intrinsic functions as much as possible. Kris Mok (Azul Systems) did a 
> great presentation of this back in 2013 
> https://www.slideshare.net/RednaxelaFX/green-teajug-hotspotintrinsics02232013 
> <https://www.slideshare.net/RednaxelaFX/green-teajug-hotspotintrinsics02232013>
>
One of the nice things about a JVM language is that it gets better when 
other people do clever things.

Jeff

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