Java threads / JVM and CPUs

[James]

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.

 

[Oliver Wong]

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

 

[Dimitri Maziuk]

Oliver Wong sez:

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".

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

 

[Roedy Green]

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.

 

[Roedy Green]

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.