So that's what it boils down to: transactions are "free" and a wonderful way to elide those horrible expensive locks.
But only if you never make a mistake.
They are expensive as hell even for very low rates of transaction failures. And you really cannot know statically (even if you don't end up reaching some transaction limit, you may easily end up just having heavy contention on the data structures in question).
So I claim that anybody who does transactional memory without having a very good dynamic fallback is basically totally incompetent. And so far I haven't seen anything that convinces me that competence even exists in this area.
Monday, September 27, 2010
Linus on transactional memory
I want transactional memory like the next guy, but comments like this one by Linus indicate that we still have a long way to go: