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module Main where
import Control.Concurrent
import Foreign.C
import GHC.Clock
import GHC.Event
import System.CPUTime
import System.Posix.Types
foreign import ccall unsafe "socket" c_socket ::
CInt -> CInt -> CInt -> IO CInt
makeTestSocketFd :: IO Fd
makeTestSocketFd = do
sockNum <-
c_socket
1 -- PF_LOCAL
2 -- SOCK_DGRAM
0
return $ (fromIntegral sockNum :: Fd)
callback :: FdKey -> Event -> IO ()
callback _ _ = return ()
-- Idle CPU usage with 0 for 0% and 10^12 for 100%
idleCpuUsage :: IO Double
idleCpuUsage = do
startTime <- getMonotonicTime
startCPUTime <- getCPUTime
threadDelay 5000000
endCPUTime <- getCPUTime
endTime <- getMonotonicTime
return $ fromIntegral (endCPUTime - startCPUTime) / (endTime - startTime)
main :: IO ()
main = do
(Just eventMgr) <- getSystemEventManager
fd <- makeTestSocketFd
noEventUsage <- idleCpuUsage
registerFd eventMgr callback fd evtRead OneShot
registerFd eventMgr callback fd evtWrite OneShot
eventTriggeredUsage <- idleCpuUsage
-- CPU consumption should roughly be the same when just idling vs
-- when idling after the event been triggered
print $ eventTriggeredUsage / noEventUsage < 100.0
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