MVarBenchmark.hs

import Control.Concurrent
import Control.Concurrent.STM
import Criterion.Main
import Data.IORef


main = do
    mv <- newMVar ()
    tv <- newTMVarIO ()
    ir <- newIORef ()
    defaultMain $
      [ bgroup "reading"
        [ bench "MVar" $ whnfIO $ readMVar mv
        , bench "TMVar" $ whnfIO $ atomically $ readTMVar tv
        , bench "IORef" $ whnfIO $ readIORef ir
        ]
      , bgroup "take/put"
        [ bench "TMVar" $ whnfIO $ atomically (takeTMVar tv) >> atomically (putTMVar tv ())
        , bench "MVar" $ whnfIO $ takeMVar mv >> putMVar mv ()
        ]
      ]

results-nonthreaded.txt

benchmarking reading/MVar
time                 1.663 ns   (1.662 ns .. 1.663 ns)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 1.660 ns   (1.658 ns .. 1.663 ns)
std dev              7.061 ps   (2.594 ps .. 14.45 ps)

benchmarking reading/TMVar
time                 22.57 ns   (22.54 ns .. 22.61 ns)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 22.50 ns   (22.48 ns .. 22.53 ns)
std dev              80.60 ps   (66.98 ps .. 98.68 ps)

benchmarking reading/IORef
time                 1.337 ns   (1.337 ns .. 1.337 ns)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 1.334 ns   (1.333 ns .. 1.335 ns)
std dev              2.163 ps   (1.630 ps .. 2.890 ps)

benchmarking take/put/TMVar
time                 54.18 ns   (54.16 ns .. 54.20 ns)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 54.07 ns   (54.04 ns .. 54.09 ns)
std dev              92.54 ps   (76.48 ps .. 117.0 ps)

benchmarking take/put/MVar
time                 3.789 ns   (3.788 ns .. 3.790 ns)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 3.781 ns   (3.779 ns .. 3.783 ns)
std dev              5.546 ps   (4.523 ps .. 6.762 ps)

results-threaded.txt

benchmarking reading/MVar
time                 1.683 ns   (1.682 ns .. 1.683 ns)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 1.679 ns   (1.678 ns .. 1.680 ns)
std dev              3.049 ps   (2.444 ps .. 3.893 ps)

benchmarking reading/TMVar
time                 28.28 ns   (27.96 ns .. 28.57 ns)
                     0.999 R²   (0.999 R² .. 1.000 R²)
mean                 28.16 ns   (27.98 ns .. 28.35 ns)
std dev              638.4 ps   (595.3 ps .. 698.5 ps)
variance introduced by outliers: 35% (moderately inflated)

benchmarking reading/IORef
time                 1.334 ns   (1.334 ns .. 1.335 ns)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 1.331 ns   (1.331 ns .. 1.332 ns)
std dev              1.840 ps   (1.552 ps .. 2.173 ps)

benchmarking take/put/TMVar
time                 80.83 ns   (80.82 ns .. 80.85 ns)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 80.63 ns   (80.59 ns .. 80.68 ns)
std dev              153.0 ps   (123.1 ps .. 211.7 ps)

benchmarking take/put/MVar
time                 4.672 ns   (4.671 ns .. 4.674 ns)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 4.662 ns   (4.660 ns .. 4.665 ns)
std dev              7.891 ps   (5.973 ps .. 11.45 ps)