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{-# LANGUAGE UnboxedTuples #-}
{-# LANGUAGE MagicHash #-}
module Main where
import GHC.Exts
import GHC.IO
import GHC.Stats
import System.Mem
import Control.Monad
data BA = BA ByteArray#
-- TODO: This shouldn't be hardcoded but MBLOCK_SIZE isn't exported by
-- any RTS header I could find.
mblockSize = 2 ^ 20
main = do
-- Increasing this number increases the amount of fragmentation (but not
-- linearly)
ba <- replicateM 500 one
replicateM 100 performMajorGC
s <- getRTSStats
let mblocks = (gcdetails_mem_in_use_bytes (gc s) `div` mblockSize)
if mblocks < 15
then return ()
else error ("Heap is fragmented: " ++ show mblocks)
return ()
one = do
ba <- mkBlock
bs <- mapM isP ba
return ()
isP (BA ba) = IO $ \s0 -> (# s0, isTrue# (isByteArrayPinned# ba) #)
mkN 0 = return []
mkN k = (:) <$> mkBA <*> mkN (k - 1)
-- Mixture of pinned and unpinned allocation so that allocatePinned takes
-- some pinned blocks from the nursery.
mkBlock = (++) <$> replicateM 100 mkBAP <*> replicateM 10000 mkBA
mkBAP =
IO $ \s0 ->
-- 1024 is below large object threshold but fills up a block quickly
case newPinnedByteArray# 1024# s0 of
(# s1, mba #) -> case unsafeFreezeByteArray# mba s1 of
(# s2, ba #) -> (# s2, BA ba #)
mkBA =
IO $ \s0 ->
-- 1024 is below large object threshold but fills up a block quickly
case newByteArray# 1024# s0 of
(# s1, mba #) -> case unsafeFreezeByteArray# mba s1 of
(# s2, ba #) -> (# s2, BA ba #)
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