ReentrantLock performance regression between JDK5 and 6/7?

[Florian Weimer]

* Tom Rodriguez:

> I believe this was caused by the switch to using lock addl[esp], 0
> instead of mfence for volatile membars, 6822204.  My review request
> for that said that at the time I didn't measure any performance change
> for Intel, http://cr.openjdk.java.net/~never/6822204.  On your
> microbenchmark I can measure the difference though so I'm going to
> remeasure derby which previously showed the big difference.  We may
> want to make the lock addl be AMD specific.

Couldn't the relative speed of the two instructions also depend on the
type of benchmark?

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