Chris Price wrote:
>
> SUMMARY
> So even if your Java program is threaded, the bottleneck is still the
> single-process JVM, reducing your gain on SMP systems from threading to
> none. Optimization of many threads within the JVM itself is quite good
> from what I have read.
>
<kidding>
<flamemode enabled="false">
It depends on your JVM implementation... Older VMs were a
one-monolithic-process VMs, so threads created "within" the JVM, were
not seen by the kernel, and so you couldn't get benefits from SMP
architectures. These are called GREEN THREADS...
Solaris, anyway, supports SMP and threads, and in these last months also
Linux (w/ kernel 2.2) can take advantage of SMP architectures (threads,
or "lightweight processes" were a feature of kernel 1.2.something
AFAIK)...
With newer JVMs (like Blackdown JDK 1.1.7 or 1.2 WITH native threads
support, and the native threads implementation of Sun's JDK 1.1/1.2),
you actually benefit from kernel-scheduled (and managed) threads. What
does it mean? that whenever you call new Thread() a "kernel" thread (and
not a GREEN one) is now created, and so, yes, you can benefit from SMP
architecture...
A positive note (?) comes also from the Microsoft OSs (WinNT). Windows
NT supports (since 3.1 release) the SMP architectures and threads. And
sun's JVM supports ONLY native threading under Win32 environment, so, if
you have an NT box, and a JVM, this one uses the full power of your SMP
architecture (even if in a bugged microsoftish way :-)
Pier
</flamemode>
</kidding>
--
Pierpaolo Fumagalli - Java Apache Project - <http://java.apache.org/>
E-Mail <mailto:[EMAIL PROTECTED]> <mailto:[EMAIL PROTECTED]>
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