Subject: HotSpot is out?

From: [email-masked] (Omer F Rana)
Date: Tue, 18 May 1999 12:25:38 +0100 (BST)

Hi, 

Sun's Java HotSpot performance engine -- using compiler optimisations
to improve performance is now out. A Windows NT version is downloadable
from: 

http://www.javasoft.com/features/1999/04/hotspot.html

Anyone tried it yet? Any comments? Interesting that there is no download
available for Solaris! (Sun's own OS).

regards
Omer

-- 
work:+44 (0)1222-875542 / otherwise:+44 0956-299981 / parallel and scientific 
computing group / room S2.03 / dept of computer science / university of wales
- cardiff / po box 916 / cardiff cf2 3xf / uk / email: [email-masked]

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From: Wolfgang HOSCHEK <[email-masked]>
Date: Tue, 18 May 1999 17:25:32 +0200

It's been there for quite some time now. The Solaris version is said to
ship in June or July (forgot it). I tried the Windows version - don't
expect too much.
You might see some moderate speedup for some apps, no speedup for many
apps and even slowdowns for some other apps, very much depending on the
use case.

Preliminary impressions (not based on extensive tests, don't take them
too seriously):

- Unblocking synchronized method calls are now only 5 times slower than
unsynchonized method class. This is a real improvement, but still they
are not quite there yet.

- Inlining doesn't seem to be exploited that much. Not many other
optimizations seem to be employed either. The produced native code
hardly ever seems to be better than the one produced by JDK 1.2 classic
(SymJit).

- If you have a method that is CPU intensive (e.g. looping 10000000
times over some statements), Hotspot will not switch from interpreted
code to native code *while* executing this method, only after having
finished executing the method. One needs to "warm up" (artificiallty
trigger JIT compilation) before using the method for something
expensive. Hotspot V2.0 is said to be able to switch during method
execution, alleviating this problem.

- The cost of feedback is difficult to estimate. Benchmarking is
difficult. The dynamic nature of execution can yield timings with large
variance.

- Running VolanoMark locally with Hotspot is a tiny little bit slower
than with JDK1.2 Win classic VM, as far as I can see here.
(java [-classic] -ms8m -mx64m COM.volano.Mark -count 10 and
java [-classic] -ms8m -mx64m COM.volano.Main)

- GC is really quick.

- IBM Win 1.1.7 is a real competitor.

In short: HotspotV1.0 is interesting and sometimes useful, but no great
breakthrough. The technology is certainly cool, but doing adaptive
compilation is a tough business.

Wolfgang.

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From: "Thomas Maslen" <[email-masked]>
Date: Wed, 19 May 1999 18:36:10 +1000

As long as we're talking about systems to make Java go faster, I'd be
interested (though I'm not sure whether this list is) in hearing about
people's experiences with the various native-code compilers -- TowerJ,
Jove (Instantiations), BulletTrain (NaturalBridge), and I think there's
an IBM one.  I'd particularly like to take BulletTrain (www.naturalbridge.com) 
for a spin, but it'll be a while before I find the time and I need to scare 
up a Windows NT box, so any info that other people have would be helpful.

Thomas Maslen
[email-masked]

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From: "Thomas Maslen" <[email-masked]>
Date: Fri, 21 May 1999 13:52:29 +1000

> ship in June or July (forgot it).

One thing that may be newer is a Release Candidate 1 for Solaris/SPARC.

It's on the Java Developer Connection, with their home-grown password 
nonsense, but it is there.  (It looks as though perhaps it has been there
since April 23, but the link from the public HotSpot page is new).  See

		http://java.sun.com/products/hotspot/

and the "New!" paragraph near the bottom.

Thomas Maslen
[email-masked]