On Sat, 12 Jun 2010, Joachim Geidel wrote:

> While testing JNIPort on Pharo 1.0 and Pharo 1.1, I noticed that in Pharo
> 1.0, a JVM (a wrapper object for the Java Virtual Machine) could be
> initialized in ca. 4 seconds, while this needed 11 to 12 seconds in Pharo
> 1.1. When I profiled the JVM startup in 1.1, the profile reported that less
> than 20% of the time was spent there; the rest was not accounted for in the
> report.
>
> In Squeak 4.1, I encountered a deadlock problem related to Squeak's current
> WeakRegistry implementation when the JVM is started. This problem
> disappeared when I changed the finalizationProcess of WeakArray such that it
> runs at systemBackgroundPriority instead of userBackgroundPriority.
>
> Applying the same change to Pharo 1.1 makes a big difference. The JVM starts
> in 4.4 seconds, approximately matching the time it takes in Pharo 1.0.
>
> Starting the JVM in Squeak 4.1 is about 20% faster than Pharo 1.1. As the
> difference is in the part which is not accounted for by the time profiler,
> it is probably due to the differences in the implementation of
> WeakIdentityKeyDictionary which have an impact on the performance of the
> finalizationProcess.
>
> I am not sure if changing the priority of the finalizationProcess could
> possibly break something, and I also do not yet understand why changing the
> priority makes such a big difference both in Squeak and Pharo.

I think normal processes (with priority 40) could starve the finalization 
process if it's priority were <= 40 (#systemBackgroundPriority is 20).

>
> How should this issue be handled? Should I add this as issues to the bug
> tracking tools for Pharo and Squeak respectively?

I uploaded a fix to the Inbox: Collections-ul.362. If you're using a Trunk 
image, just update it and load this package to your image. If you're using 
a stock 4.1 image, then the easiest way to get the fix, is to add the 
following line to the end of WeakKeyDictionary >> #finalizeValues

cleanUpAfterRemove ifTrue: [ self fixCollisionsFrom: array size ]

If you have the time, please check if this fixes the issue for Squeak.


Levente

>
> Cheers,
> Joachim Geidel
>
>
>
>