Re: optimizing synchronization

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From: Godmar Back (gback@cs.utah.edu)
Date: Wed Jan 13 1999 - 14:54:48 EST


>
> Godmar Back writes:
> > This is possible because MONITOR_ENTER and MONITOR_EXIT always occur in pairs.
> > However, it will require changes to the JIT to store the address of the
> > lock returned from MONITOR_ENTER somewhere, presumably on the stack.
>
> I remember hearing about some talk (Sun? IBM?) that described
> doing exactly this: they made the same observation, ie, that
> monitor lock information naturally can be stored on the stack,
> since Java locks are really 'stack based'. The implication was
> that this was a clever thing to do and was a win.
>

 Let's hope they don't hold a patent.

I actually remembered that Sun said they would make "synchronization
practically free" and "exploit the symmetry". So I discussed this
yesterday with Pat and we oracled on what they might be doing, and
this is what we come up with.

        - Godmar


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