Hi, I am preparing a talk about the details of how data and programs look in memory in Haskell (well, GHC). When explaining the memory consumption of a large String, I wanted to show the effect of short-int-replacement that happens in http://hackage.haskell.org/trac/ghc/browser/rts/sm/Evac.c#L550
I use my ghc-heap-view-package to observe the heap. This programs shows
the effect:
import GHC.HeapView
import System.Mem
main = do
let hallo = "hallo"
mapM_ (\x -> putStrLn $ show x ++ ": " ++ show (asBox x))
hallo
performGC
mapM_ (\x -> putStrLn $ show x ++ ": " ++ show (asBox x))
hallo
gives, as expected:
$ ./SmallChar
'h': 0x00007f2811e042a8/1
'a': 0x00007f2811e08128/1
'l': 0x00007f2811e09ef0/1
'l': 0x00007f2811e0bcd8/1
'o': 0x00007f2811e0db10/1
'h': 0x00000000006d9bd0/1
'a': 0x00000000006d9b60/1
'l': 0x00000000006d9c10/1
'l': 0x00000000006d9c10/1
'o': 0x00000000006d9c40/1
but in GHCi, it does not work:
$ runhaskell SmallChar.hs
'h': 0x00007f5334623d58/1
'a': 0x00007f5334626208/1
'l': 0x00007f5334627fc0/1
'l': 0x00007f5334629dc0/1
'o': 0x00007f533462bba8/1
'h': 0x00007f533381a1c8/1
'a': 0x00007f5333672e30/1
'l': 0x00007f533381a408/1
'l': 0x00007f533381a6b8/1
'o': 0x00007f533389c5d0/1
Note that the GC does evacuate the closures, as the pointers change. Why
are these not replaced by the static ones here?
Thanks,
Joachim
--
Joachim "nomeata" Breitner
[email protected] | [email protected] | GPG: 0x4743206C
xmpp: [email protected] | http://www.joachim-breitner.de/
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