Yes, I do. But binding might not be the top priority since I'd like to
leave logic in Haskell.
Tried the dir checking, could not see major differences.
On Fri, May 10, 2019 at 10:13 AM Vanessa McHale
Would you happen to have the Rust/C code available?
One option is to simply using the C code and bind to it.
The one thing that stands out to me in your code is that you call
doesDirectoryExist
as well as
getFileStatus
when you could determine whether it exists with
doesPathExist
and then determine whether it's a directory by checking the result of getFileStatus
Cheers, Vanessa McHale
On 5/9/19 9:00 PM, Magicloud Magiclouds wrote:
Hi, I have asked this in Stackoverflow without getting an answer. Wondering if people here could have some thoughts.
I have a function reading the content of /proc every second. Surprisingly, its CPU usage in top is around 5%, peak at 8%. But same logic in C or Rust just takes like 1% or 2%. Wondering if this can be improved. /proc is virtual filesystem, so this is not related to HDD performance. And I noticed this difference because my CPU is too old (Core Gen2). On modern CPU, as tested by others, the difference is barely noticeable.
import Control.Exception import Control.Concurrent import Control.Monad import Data.Char import Data.Maybe import System.Directory import System.FilePath import System.Posix.Files import System.Posix.Signals import System.Posix.Types import System.Posix.User import System.IO.Strict as Strict
watch u limit0s limit0h = do listDirectory "/proc/" >>= mapM_ (\fp -> do isMyPid' <- maybe False id <$> wrap2Maybe (isMyPid fp u) wrap2Maybe (Strict.readFile ("/proc/" fp "stat"))) threadDelay 1000000 watch u limit0s limit0h where wrap2Maybe :: IO a -> IO (Maybe a) wrap2Maybe f = catch ((<$>) Just $! f) (\(_ :: IOException) -> return Nothing) isMyPid :: FilePath -> UserID -> IO Bool isMyPid fp me = do let areDigit = fp >= "0" && fp <= "9" isDir <- doesDirectoryExist $ "/proc/" fp owner <- fileOwner <$> getFileStatus ("/proc" fp) return $ areDigit && isDir && (owner == me)
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