Re: java.util.Hashtable.size()/isEmpty()

[Bryce McKinlay]

Etienne M. Gagnon wrote:

> Artur Biesiadowski wrote:
>
> > First - removing as much synchronization as possible, while staying 
> > compatible is certainly a good thing. Synchronizing is _really_ costly - 
>
>
> Have you heard of "thin locks" and other VM level optimizations that 
> reduces "significantly" the cost of locks?  Do not compute the cost of 
> locks based on their implementation in Sun's old JDK, or based on an 
> implementation that does not implement state-of-the-art techniques. 


Synchronization techniques have improved, however it will always be slow 
(relative to other operations) in a multithreaded/multiprocessing 
environment, because it cannot be done without some form of spinlocking 
or memory bus synchronization. The only way to truely make it fast for a 
multiprocessor would be to come up with some magic bus architechture 
which is as fast as the cpu cores!

> Systems like "HotSpot/Jalapeno" are getting to the point where the are 
> able to identify things like "single threaded programs" and thus 
> eliminate all lock operations when possible. 


Yes. But remember that many of the applications that are hurt most by 
synchronization (AWT, Swing) are never single threaded.

regards

Bryce.