Retainer profiling -- too slow?

[Simon Marlow]

Tim Chevalier wrote:
> Hi all,
> 
> Are there any known problems with retainer profiling in GHC 6.8.2? I
> have a program that takes 3 minutes to run with "normal" profiling
> enabled (+RTS -P -RTS), but with +RTS -P -hr -RTS, it's 20 minutes and
> counting. I can tell that progress is being made since the .hp file
> keeps getting bigger, but that seems like a lot of overhead.
> 
> I can try to come up with a smaller test case if necessary; just
> wanted to see if there's any known problem.

It certainly is slow, especially with large heaps, because IIRC it has to 
do multiple traversals of the heap.  The +RTS -sstderr output will tell you 
how much time is spent doing retainer profiling.  (also retainer profiling 
is often not terribly useful IMO).

Cheers,
	Simon