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module Main where
import Control.Concurrent
import Foreign.C
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 ()
idleCpuUsage :: IO Integer
idleCpuUsage = do
startCPUTime <- getCPUTime
threadDelay 500000
endCPUTime <- getCPUTime
return $ endCPUTime - startCPUTime
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 $ (fromIntegral eventTriggeredUsage / fromIntegral noEventUsage) < 2.0
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