Current Status

[Jon Olson]

On Thu, 18 Feb 1999, Godmar Back wrote:

>
>Apropos sync_info.  EF has gone public since the last discussion on this
>topic on this list.  While I don't have hard numbers, I think that their 
>way of doing synchronization is the best I've seen so far.
>
>The basic idea is that they spent an additional word per object, but 
>unlike gcj/kaffe, they spend 30 bits of it to store an object's hashcode
>(Kaffe uses the address of an object, which doesn't work with a moving 
>collector - what does gcj/libjava do?), and they spend 2 bits to indicate
>that an object is locked/that the lock is contended.  This optimizes
>the common case of taking an uncontended lock.
>
>	- Godmar

Hmm.... I'd be interested in seeing an implementation of this synchronization
strategy.  I suppose that the only time it would allocate a synchronization
object is in the case an object is already locked.  Off the top of my head, I
can't see how to easily know if I already own the monitor with just a
single bit to indicate that an object is locked.  Maybe I'm just dense right
now...

--
Jon Olson, Modular Mining Systems
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