HotSpot(TM) Tiered VM available in jdk1.7.0/b12 :-)

Performance Tuning
#1

Hi there,

1.) Finally the tired-jvm has made its way into the public builds and can be tested by interested developers without building Hotspot their own.

A short test with Eclipse showed:

  • Improved performance compared to client-compiler
  • No class data sharing
  • A lot of compilation is happening (code-code was 15mb 5min after start)

I guess this optimization could be really interesting for game-programmers which always fight with hotspots slow-start/fast-code or fast-start/slow-code situation.

2.) Also new in b12 are some SIMD improvements.
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6536652
Sad that the report is more or less a stub, not talking about which optimization can be performed on which CPUs :-/

lg Clemens

#2

Mmm, been waiting for that for a long time. Is EA/stack allocation in there yet too?

Cas :slight_smile:

#3

here http://blogs.sun.com/fatcatair/entry/tiered_compilation_issues you can read more about the current tiered compiler builds and why there is to much compilation happening.

#4

If it would be in, you would note the difference, wouldn’t you?

Yes I know the blog-entry. But it does not explain why code-cache is so large. It should not compile much more methods than client-compiler did.

lg Clemens

#5

a larger compiler code threshold isn’t necessarily an indicator for more compiled methods…

[quote]So part of the problem is as Damon surmised in the first question, but there is more to it than that. If you don’t adjust the thresholds (Tier2CompileThreshold) you’ll certainly do too much compilation because even though that threshold matches what server normally used the counters are being incremented by compiled code and not the interpreter and since the compiled code is faster than the interpreter we can hit the limit quicker.
[/quote]
read the older blog-entries if you want more information about the tiered compiler.

#6

yes more methods are compiled in a shorter timeframe, but the overall count of compiled methods should be the same as with client.

#7

sorry that I was so harsh - but I was a bit angry about the fact that some people can never stop complaining.
I liked to share my happyness - and what I got were rants about whats “missing”.

Never forget … hotspot is the most advanced widely used JIT/VM available :slight_smile:

lg Clemens