High memory usage after performing GC
Hello, lets consider following program:
{-# LANGUAGE NoMonomorphismRestriction #-}
import System.Mem.Weak
import Control.Concurrent
import System.Mem
data Tst a = Tst a deriving (Show, Eq)
tst a = do
let arr = [0 .. a*a*a]
v = Tst (seq arr arr)
ptr <- mkWeakPtr v Nothing
return ptr
main = do
ptrs <- mapM tst [1..100000000]
--performGC
--performMajorGC
--performMinorGC
threadDelay 1000000
xr <- mapM deRefWeak ptrs
print $ length $ filter (/= Nothing) xr
threadDelay 5000000
return ()
It simply creates 10 million of weak references to values of Tst
. These weak pointers are returned in the main function. After that we sleep a second and ask how meany references are alive. I get the 0
as a result here - so everything seems ok - garbage collection worked. There is a problem though - somehow the memory was not released, because during the last 5-second sleep the program uses over 14 Gb of RAM on my computer.
I'm compiling it simply with ghc -O2 Main.hs
. I'm pretty sure this is a bug, because such behaviour is not expected I think.