14 Aug
2014
14 Aug
'14
12:32 p.m.
I have to agree with Brandon's diagnosis: unsafePerformIO will take out a lock, which is likely why you are seeing no parallelism. Edward Excerpts from Brandon Allbery's message of 2014-08-14 17:12:00 +0100:
On Thu, Aug 14, 2014 at 11:54 AM, Christian Höner zu Siederdissen < choener@tbi.univie.ac.at> wrote:
go xs = unsafePerformIO $ do forM_ xs $ cfun return $ somethingUnhealthy
I wonder if this is your real problem. `unsafePerformIO` does some extra locking; the FFI specifies a function `unsafeLocalState`, which in GHC is `unsafeDupablePerformIO` which skips the extra locking.