How long does it take to create 1 million threads in Haskell?

from here.

import Control.Concurrentimport Control.Monadn = 100000main = do    left  <- newEmptyMVar    right <- foldM make left [0..n-1]    putMVar right 0    -- bang!    x <- takeMVar left -- wait for completion    print x where    make l n = do       r <- newEmptyMVar       forkIO (thread n l r)       return rthread :: Int -> MVar Int -> MVar Int -> IO ()thread _ l r = do   v <- takeMVar r   putMVar l $! v+1

on my not quite 2.5gh laptop this takes less than a second.

set n to 1000000 and it becomes hard to write the rest of this post because the OS is paging like crazy. definitely using more than a gig of ram (didn't let it finish). If you have enough RAM it would definitely work in the appropriate 10x the time of the 100000 version.

Well according to here the default stack size is 1k, so I suppose in theory it would be possible to create 1,000,000 threads - the stack would take up around 1Gb of memory.

Using the benchmark here, http://www.reddit.com/r/programming/comments/a4n7s/stackless_python_outperforms_googles_go/c0ftumi

You can improve the performance on a per benchmark-basis by shrinking the thread stack size to one that fits the benchmark. E.g. 1M threads, with a 512 byte stack per thread, takes 2.7s

$ time ./A +RTS -s -k0.5k