More performance explorations

[John Rose]

On May 26, 2011, at 4:53 PM, Charles Oliver Nutter wrote:

> On Thu, May 26, 2011 at 5:20 AM, Rémi Forax <forax at univ-mlv.fr> wrote:
>> As far as I know there is no specific optimization of SwitchPoint
>> i.e there is still a volatile read in the middle of the pattern.
> 
> If that's true I'm not sure how this is better than a regular GWT with
> a volatile read in the test.

It's probably about the same as GWT+volatile right now; actually there's a MCS with a memory barrier in the present code.

But since SwitchPoint is a clear pattern it can be optimized in the future.  It's clear the user of a SwitchPoint wants cheap infrequent inter-thread communication, and volatiles won't give that as easily as an intrinsic known to the JVM.

-- John
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