Any Real-World Experience Using Software Transactional Memory?

We use it pretty routinely for high concurrency apps at Galois (in Haskell). It works, its used widely in the Haskell world, and it doesn't deadlock (though of course you can have too much contention). Sometimes we rewrite things to use MVars, if we've got the design right -- as they're faster.

Just use it. It's no big deal. As far as I'm concerned, STM in Haskell is "solved". There's no further work to do. So we use it.

I participated in the hobbyist development of the BitTorrent client in Haskell (named conjure). It uses STM quite heavily to coordinate different threads (1 per peer + 1 for storage management + 1 for overall management).

Benefits: less locks, readable code.

Speed was not an issue, at least not due to STM usage.

Hope this helps

The article "Software Transactional Memory: Why is it Only a Research Toy?" (Călin Caşcaval et al., Communications of the ACM, Nov. 2008), fails to look at the Haskell implementation, which is a really big omission. The problem for STM, as the article points out, is that implementations must chose between either making all variable accesses transactional unless the compiler can prove them safe (which kills performance) or letting the programmer indicate which ones are to be transactional (which kills simplicity and reliability). However the Haskell implementation uses the purity of Haskell to avoid the need to make most variable uses transactional, while the type system provides a simple model together with effective enforcement for the transactional mutation operations. Thus a Haskell program can use STM for those variables that are truly shared between threads whilst guaranteeing that non-transactional memory use is kept safe.