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From "Sergey Salishev" <sergey.i.salis...@gmail.com>
Subject Re: JRE Lite
Date Mon, 28 Apr 2008 19:17:06 GMT
Hi,

Alexey, thanks for the link. I don't think the distribution size is the
biggest JRE problem for client applications. Anyway even without Kernel
distribution RE JRE is only 15MB which is substantially smaller than .NET
framework redistributable. With the Kernel distribution it's only 3MB about
2x Flash Player size :)

JRE's three biggest problems I think are slow startup, large footprint and
GC pauses. The footprint problem is generally solved by data sharing between
JVM instances. The GC pauses can be helped by using incremental or
concurrent GC.

The startup time tougher problem. It's almost unrelated to the ditribution
size as only the used classes are loaded. But it's governed by the class
parsing and no-opt JIT/interpreter overhead. It's possible to make JRE
startup to be more lean and mean. But the real answer here is excluding the
classloading and JIT phase from startup altogether at least for frequently
used components.  The good news are that most of the frequently used classes
for small applications are located in class libraries. RE JRE as I remember
already can precompile rt.jar and use that fact. .NET has a signed binary
module cache and the application installer can compile the model AOT and
place it to cache.

The bbiggest  problems of AOT compiled module caching are class versioning
and security. I think it's possible to implement such mechanism for Java
using Jar files as an atomic modules for AOT caching. In this case the Jar
signature would be used for module versioning and ensuring the binary code
is unmodified. We already made some experiments and caching on individual
method level doesn't give any performance boost due to class loading and
signing overhead.

Thanks.
Sergey.

2008/4/28 Alexey Petrenko <alexey.a.petrenko@gmail.com>:

>
> http://java.sun.com/developer/technicalArticles/javase/java6u10/index.html#kernel
>

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