#4262: GHC's runtime never terminates unused worker threads
---------------------------------+------------------------------------------
Reporter: Remi | Owner:
Type: bug | Status: new
Priority: normal | Component: Runtime System
Version: 6.12.3 | Keywords: worker thread foreign function
interface
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: Runtime performance bug
---------------------------------+------------------------------------------
When concurrently calling safe FFI functions, worker OS threads are
created. These threads then never quit.
The following toy program creates 30k OS threads (which is fine because
that's exactly what it asks for) which are then never "garbage collected":
30k threads and over 230g of VM are hanging around until the program
exits.
{{{
{-# LANGUAGE ForeignFunctionInterface #-}
module Main where
import Control.Concurrent
import Control.Monad
import Foreign.C.Types
import System.Mem
foreign import ccall safe sleep :: CUInt -> IO ()
main = do
replicateM_ 30000 $ forkIO $ sleep 2
getLine
-- do other stuff
}}}
P.S. Of course I should simply use threadDelay in this case. The real
program performs up to a few hundred concurrent fdatasync calls.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4262>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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