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Transactional Memory

Transactional Memory

Posted Jun 11, 2009 8:24 UTC (Thu) by ketilmalde (guest, #18719)
In reply to: Transactional Memory by wahern
Parent article: A look at two new languages: Vala and Clojure

> Everybody talks about how STM removes locking. This is bollocks.

Really? I think there's a lot of talk about how STM is bollocks. While I haven't read the literature (as) extensively (as you seem to have), I've yet to see any rationale for this. More specific pointers than just a ream of research paper titles would be great.

> This is because pure STM requires the LL/SC

I'm sorry, but isn't this SOFTWARE transactional memory we're talking about? What's stopping the run-time system from abstracting away the underlying hardware?

> Every existing STM library actually uses locks internally. Period.
> Please, stop the cargo cult hyperbole. The only real STM implementations
> are on paper, or maybe in a lab w/ a custom ASIC.

While I've only made toy implementations using it, Haskell's STM library seems awfully real to me. I'm not aware of any locking, but I could be misunderstanding how it works, of course.

Further down, you go on to claim:

> Fact is, real STM does not exist.

and

> Everything else can deadlock, and can livelock

While I love unsubstianted claims as much as the next guy, your opinions would be more enlightening if you provide actual example code that demonstrates this.


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