-Xconcurrentio

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villo - 01 Mar 2007 08:43 GMT

Hi all

reading
http://java.sun.com/docs/hotspot/HotSpotFAQ.html

I don't quite understand what could be the benefit of using this
option
on a Linux system. Is there anyone here that knows what

"-Xconcurrentio can still help since it turns on some other internal
options."

actually means?

Thanks a lot,
Francesco

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Arne Vajhøj - 02 Mar 2007 01:19 GMT

> reading
> http://java.sun.com/docs/hotspot/HotSpotFAQ.html
>
> I don't quite understand what could be the benefit of using this
> option
> on a Linux system. Is there anyone here that knows what

Only Solaris is mentioned, so probably there are no benefits of
this for Linux.

> "-Xconcurrentio can still help since it turns on some other internal
> options."
>
> actually means?

It tells the JVM something that make it do Java threads
faster.

http://java.sun.com/developer/technicalArticles/Programming/JVMPerf/

says

"This test examined the impact of the Java 2 SDK 1.3.0 EA runtime option
-Xconcurrentio on performance. Specifying -Xconcurrentio changes the
implementation of thread synchronization in a way that sometimes
improves throughput for programs having many threads blocking
Input/Output. The gains are due to a higher level of concurrency in the
Solaris operating system kernel."

http://www.volano.com/report/

says

"In particular, the Solaris HotSpot VM has an option called
-Xconcurrentio. It apparently does two things: it enables lightweight
process-based (LWP-based) synchronization rather than the Solaris
thread-based synchronization, and it disables thread-local allocation
buffers (TLABs). LWP-based synchronization is the default in the Java
1.4 HotSpot VM, but must be enabled for the Java 1.3 HotSpot VM."

If you need more info I think you will need to study code.

Arne

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villo - 05 Mar 2007 11:27 GMT

Thanks Arne

actually I thought it could possibly affect other OSes as the
phrase was "particularly on Solaris."...

but given the links you cite it seems not.
Thanks for clarifying.

Francesco

> > reading
> >http://java.sun.com/docs/hotspot/HotSpotFAQ.html
[quoted text clipped - 39 lines]
>
> Arne

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