dcholmes at optusnet.com.au
Wed May 24 18:26:05 EDT 2006
> This isn't as thread safe as it would be if both were synchronized.
> Even if Thread 2 terminates, Thread 1 might not, because there is no
> happens-before edge from Thread 2's increment to Thread 1. If getCount
> were synchronized, then Thread 1 would terminate if Thread 2 did.
Huh? count is volatile.
> The class would probably be a faster read than AtomicInteger, but a
> slower write (getting a lock is slower than performing a single atomic
- reads: same
both do a LD with whatever memory barrier is needed on the
platform (which is probably none)
- uncontended: close call
AtomicInteger.get has a method call with LD and CAS plus MEMBAR
Half-sync: CAS for synchronized, LD, ST plus MEMBAR (depends if
the runtime elides the redundant MEMBARS for
- contended: Half-sync wins by avoiding ctx switches
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