Re: [Sablevm-developer] Threading support in SableVM

[Archie C. <ar...@de...>]

Chris Pickett wrote:
> > The inflating of the "other" locks is to avoid this inefficiency.
> > But it's not necessary to do this for threads waiting on the actual
> > lock being released, because you do indeed want those thread to
> > wake up.
> 
> I understand and agree with most if not all of that, certainly 
> pertaining to the other locks.  I guess I was wondering, wouldn't things 
> be *faster* if you inflated the actual released thin lock, because you 
> wouldn't have to take the (what I assumed/am assuming to be slow) 
> inflation path for that lock again when future contention arose? 

A lock can only be inflated once. So it's never slower to delay this
inflation to a later point.

But more importantly, the inflation does not necessarily have to happen.
When thread #1 releases the thin lock, it wakes up thread #2. Then
thread #2 retries its lock acquisition "from the beginning". If no other
threads beat it out, then thread #2 sees an unlocked thin lock and
acquires it using compare-and-swap. So no inflation takes place in this
case.

-Archie

__________________________________________________________________________
Archie Cobbs      *        CTO, Awarix        *      http://www.awarix.com