[concurrency-interest] Nice video interview with Tim Harris andSimon Peyton-Jones

Brian Goetz brian at quiotix.com
Thu Dec 28 13:13:15 EST 2006


> Hmmm.  I remember people bitching about GC performance, but not 
> usability.  

I remember people bitching about unreliability, too, though those were 
mostly out of ignorance.  FUD items like pointers hidden from the 
collector (newP = p XOR 0xCAFEBABE; p=0) and cyclical data structures 
that can't be reclaimed by reference counting.

> I'm saying that the transaction model is not as easy to 
> program to as it appears, and it does not free you from thinking about 
> locks (in my experience with Encina and Camelot).  Did people bitch 
> about the usability of GC?

A sufficiently large quantitative difference becomes a qualitative 
difference.  If the performance is so poor, you'll do all sorts of 
things to avoid using it, and then its as if you don't have it, and you 
bitch about that.

People understand "one big fat lock".  People don't use OBFL because 
they are convinced the performance would suck.  If we could make the 
performance of OBFL better, I think many of the usability issues go away 
_relative to the current audience_.

But, of course, once you make things easier, the audience grows, and the 
new expanded audience might not see the subtleties of "don't do I/O in 
atomic blocks" and things like that.

I don't want to come off as having drank the kool-aid -- I think there's 
a long way to go before STM is real (though the Azul implementation is a 
nice proof for the concept) -- I just think that many of the arguments 
raised against it are the same as those that have been raised against 
many other fledgling technologies that we've since come to love.  I am 
anxiously hoping the research boys come up with something good here, 
because what we've got now is a bunch of bananas.




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