Hi,

Please review this patch to ensure that a parallel stream obeys the parallelism 
of a custom fork join pool when it is executed within that pool:

  
http://cr.openjdk.java.net/~psandoz/jdk10/JDK-8190974-par-stream-custom-pool/webrev/
 
<http://cr.openjdk.java.net/~psandoz/jdk10/JDK-8190974-par-stream-custom-pool/webrev/>

Streams currently do not support capabilities to control the level of 
parallelism and therefore resources utilised (tricky API design problem to get 
right). 

At the moment the trick is to run stream executions within a custom pool, 
however the number of fork join tasks created will be in proportion to the 
parallelism of the common pool thus the execution will be over-provisioned. 
This can be especially noticeable on large machines with many cores.

Paul.

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