#650: Improve interaction between mutable arrays and GC
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Reporter: simonmar | Owner: simonmar
Type: bug | Status: new
Priority: normal | Milestone: 6.12.2
Component: Runtime System | Version: 6.4.1
Resolution: | Keywords:
Difficulty: Difficult (2-5 days) | Os: Unknown/Multiple
Testcase: | Architecture: Unknown/Multiple
Failure: Runtime performance bug |
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Changes (by simonmar):
* milestone: 6.14.1 => 6.12.2
Comment:
Fixed:
{{{
Thu Dec 17 14:42:28 PST 2009 Simon Marlow <[email protected]>
* Fix #650: use a card table to mark dirty sections of mutable arrays
The card table is an array of bytes, placed directly following the
actual array data. This means that array reading is unaffected, but
array writing needs to read the array size from the header in order to
find the card table.
We use a bytemap rather than a bitmap, because updating the card table
must be multi-thread safe. Each byte refers to 128 entries of the
array, but this is tunable by changing the constant
MUT_ARR_PTRS_CARD_BITS in includes/Constants.h.
M ./compiler/codeGen/CgPrimOp.hs -2 +14
M ./includes/Cmm.h +3
M ./includes/HaskellConstants.hs +3
M ./includes/mkDerivedConstants.c +1
M ./includes/rts/Constants.h +7
M ./includes/rts/storage/ClosureMacros.h -1 +29
M ./includes/rts/storage/Closures.h +2
M ./rts/PrimOps.cmm -5 +23
M ./rts/Weak.c -2 +9
M ./rts/sm/Scav.c -54 +123
}}}
I benchmarked this program, amongst others:
{{{
import Control.Monad
import qualified Data.HashTable as H
import System.Environment
main = do
[size] <- fmap (fmap read) getArgs
m <- H.new (==) H.hashInt
forM_ [1..size] $ \n -> H.insert m n n
v <- H.lookup m 100
print v
}}}
for size=1000000, with 6.12.1 it takes around 50s on my x86/Linux laptop,
with the HEAD and this patch it takes 9.5s.
We could merge this into 6.12.2 after more testing and benchmarking, as
the changes are fairly localised.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/650#comment:24>
GHC <http://www.haskell.org/ghc/>
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