JRuby invokedynamic updates for November

[Charles Oliver Nutter]

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