help wrt semantics / primops for pure prefetches

Simon Marlow marlowsd at
Thu Nov 27 09:36:41 UTC 2014

I haven't been watching this, but I have one question: does prefetching 
actually *work*?  Do you have benchmarks (or better still, actual 
library/application code) that show some improvement?  I admit to being 
slightly sceptical - when I've tried using prefetching in the GC it has 
always been a struggle to get something that shows an improvement, and 
even when I get things tuned on one machine it typically makes things 
slower on a different processor.  And that's in the GC, doing it at the 
Haskell level should be even harder.


On 22/11/2014 05:43, Carter Schonwald wrote:
> Hey Everyone,
> in
> and
> is some preliminary work to fix up how the pure versions of the prefetch
> primops work is laid out and prototyped.
> However, while it nominally fixes up some of the problems with how the
> current pure prefetch apis are fundamentally borken,  the simple design
> in D350 isn't quite ideal, and i sketch out some other ideas in the
> associated ticket #9353
> I'd like to make sure  pure prefetch in 7.10 is slightly less broken
> than in 7.8, but either way, its pretty clear that working out the right
> fixed up design wont happen till 7.12. Ie, whatever makes 7.10, there
> WILL have to be breaking changes to fix those primops for 7.12
> thanks and any feedback / thoughts appreciated
> -Carter
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