Perf regression since b72

[Christian Thalinger]

On Mar 30, 2013, at 1:56 AM, Charles Oliver Nutter <headius at headius.com> wrote:

> I've been fiddling about with performance a bit again recently, and have noticed a perf degradation since b72. I mentioned this to the Nashorn guys and Marcus discovered that InlineSmallCode=2000 helped them get back to b72 performance. I can confirm this on JRuby as well, but in any case it seems that something has regressed.
> 
> Here's some numbers with JRuby. Numbers are for b72, hotspot-comp, and hotspot-comp with InlineSmallCode=2000. You can see that current hotspot-comp builds do not perform as well as b72 unless that flag is passed.
> 
> https://gist.github.com/headius/de7f99b52847c2436ee4
> 
> I have not yet started to explore the inlining or assembly output, but I wanted to confirm that others are seeing this degradation.
> 
> My build of hotspot-comp is current.
> 
> I do have some benchmarks that look fine without the additional flag (neural_net, for example), so I'm confused what's different in the degraded cases.

I'm not sure if Marcus talked to you already about this but there are two fixes that caused this regression:

1.  http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8007439

which was fixed by:

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8010222

in HS25-b24.

2.  We turned off tiered compilation:

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8005811

The InlineSmallCode=2000 is a way to work around the tiered slowdown.

-- Chris

> 
> - Charlie
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