Hello Neil, Tuesday, April 7, 2009, 2:25:12 PM, you wrote:
The problem I'm trying to solve is running system commands in parallel.
"system commands" means execution of external commands or just system calls inside Haskell?
Running a benchmark of issuing 1 million trivial tasks (create, modify, read and IO ref) the version without any parallelism is really fast (< 0.1 sec), and the version with parallelism is slow (> 10 sec). This could be entirely due to space leaks etc when queueing many tasks.
i think it's just because use of MVar/Chan is much slower than IORef activity. once i checked that on 1GHz cpu and got 2 million withMVar-s per second i don't understood exactly what you need, but my first shot is to create N threads executing commands from channel: para xs = do done <- newEmptyMVar chan <- newChan writeList2Chan chan (map Just xs ++ [Nothing]) replicateM_ numCapabilities $ do forkIO $ do forever $ do x <- readChan chan case x of Just cmd -> cmd Nothing -> putMVar done () takeMVar done -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com