JRuby invokedynamic updates for November

[Charles Oliver Nutter]

I should add that if you're running this against a u2ish build and
seeing poor performance, we need to talk. I'm not seeing that locally,
and you shouldn't see it either.

- Charlie

On Wed, Nov 30, 2011 at 2:42 PM, Charles Oliver Nutter
<headius at headius.com> wrote:
> On Wed, Nov 30, 2011 at 2:03 PM, Stephen Bannasch
> <stephen.bannasch at deanbrook.org> wrote:
>> Hi Charlie,
>>
>> Is your latest work going on in the indy_update branch?
>
> No, that's old stuff. I should wipe it out. I can explain your perf
> issue below, though.
>
>> I have a simple Ruby xml processing benchmark that compares several Ruby XML libraries including rexml which is part of the
>> Ruby standard library.
>>
>> My test measures the time to do the following 100 times:
>>
>> - open 98k XML document and count one type of leaf element (466 entries)
>>
>> On the latest master version of JRuby the performance of rexml degrades dramatically using Java 1.7 and even more using mlvm.
> ...
>> Using the indy_update branch of JRuby however I get MUCH better results on 1.7
>
> I'll take a guess and say you're running this against OpenJDK 7 GA,
> right? The GA release was feature-complete, but a number of indy
> features were implemented in weakly-optimized or unoptimized ways. For
> example, a *critically* important feature for JRuby's invokedynamic
> support -- SwitchPoint -- is just a full-on volatile read every time
> you traverse the guard. I could enumerate the other issues with the GA
> release's optimzation, but if you poke around the bug listings for u2
> you'll see the important JSR-292 improvements...most of which were
> initiated by my performance testing in JRuby.
>
> If you use one of the Java 7u2 early access releases (and there's
> builds of them called "OpenJDK 8" for OS X now) you should see
> substantially better performance across the board.
>
> - Charlie