On 26 January 2005 16:42, S. Alexander Jacobson wrote:
On Wed, 26 Jan 2005, Simon Marlow wrote:
When using the ordinary 2-generation collector, memory in use will tend to be 2-3 times larger than the actual residency, because this is a copying collector.
Ok. Perhaps you want a different name for this item in the reports?
Well, "memory in use" is pretty accurate - it measures the actual amount of memory that the runtime has allocated from the OS. "residency" is a GC term which refers to the amount of live data. I don't think these terms are that confusing, but perhaps my explanation was?
On the other hand, I found 10mb, 5mb, and 2.5mb maximum residency, but that is still ~100 bytes per record.
But 100 bytes per record in a (Map Int Int) seems awefully high.
That 100 bytes includes stack overhead. Remember, when you ran the heap profile which didn't show stack overhead you got a much more reasonable figure.
Lastly, I tried "example +RTS -p -K5M -hc" and then looked at the resulting graph (attachment #2) and it shows a total of 1.6Mb heap allocated and if that data is correct, it does correspond roughly to our 20-30 bytes per record estimate.
That profile doesn't include the stack, which sounds reasonable.
So I guess all the extra memory is actually being allocated on the stack rather than the heap which is a sign of a spaceleak. If I solve the spaceleak I get the 70 bytes per item back.
Yup.
I haven't looked at your code in detail, hopefully someone else can shed some light on why you're building up such a large stack in the first place.
The code is just this 6 line program:
import qualified Map zipped =zip [1..] [1..100000]::[(Int,Int)] untup f (x,y) = f x y produce = foldr (untup Map.insert) Map.empty zipped fm = length $ Map.keys produce main = print $ fm
Can someone tell me what I can do to make this more efficient?
Replace the foldr by a foldl'? import Data.List produce = foldl' (untup (flip Map.insert)) Map.empty zipped (untested) Cheers, Simon