Java threads / JVM and CPUs

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James - 16 Feb 2006 18:12 GMT

Hi, i was doing some research and was wondering if anyone had any idea
about the following:

How many active Java threads per CPU can Windows XP support?
Does it make a difference on single / dual processor boxes?

Thanks.

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Oliver Wong - 16 Feb 2006 18:44 GMT

> Hi, i was doing some research and was wondering if anyone had any idea
> about the following:
>
> How many active Java threads per CPU can Windows XP support?
> Does it make a difference on single / dual processor boxes?

One thread per core (regardless of whether the thread is a "Java thread"
or not). The other threads won't be "active". A single CPU can have multiple
cores. A core can also be "hyperhtreaded", but it's unclear as to whether
that counts as "multiple active threads", or "one thread at a time, but
really fast context switching".

- Oliver

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Dimitri Maziuk - 16 Feb 2006 20:59 GMT

Oliver Wong sez:

>> Hi, i was doing some research and was wondering if anyone had any idea
>> about the following:
[quoted text clipped - 7 lines]
> that counts as "multiple active threads", or "one thread at a time, but
> really fast context switching".

Assuming "active" means "fully independent CPU-bound", of course.
(E.g. you can expect an active I/O-bound thread to spend most of its
time waiting for I/O, while CPU is available to run another thread
-- unless it's polling in a tight loop... etfc.)

Dima

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Roedy Green - 17 Feb 2006 05:10 GMT

>How many active Java threads per CPU can Windows XP support?
>Does it make a difference on single / dual processor boxes?

the theoretical limit is RAM. Each thread eats up about 1 MB of
virtual RAM.

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Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

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Roedy Green - 17 Feb 2006 05:11 GMT

>How many active Java threads per CPU can Windows XP support?
>Does it make a difference on single / dual processor boxes?

What are threads doing? if sleep( 1000 ) you should have no trouble
filling RAM with them.

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Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

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Java threads / JVM and CPUs

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