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{- Running a long or expensive batch operation niced.
-
- Copyright 2013 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
{-# LANGUAGE CPP #-}
module Utility.Batch where
#if defined(linux_HOST_OS) || defined(__ANDROID__)
import Control.Concurrent.Async
import System.Posix.Process
#endif
{- Runs an operation, at batch priority.
-
- This is done by running it in a bound thread, which on Linux can be set
- to have a different nice level than the rest of the program. Note that
- due to running in a bound thread, some operations may be more expensive
- to perform. Also note that if the action calls forkIO or forkOS itself,
- that will make a new thread that does not have the batch priority.
-
- POSIX threads do not support separate nice levels, so on other operating
- systems, the action is simply ran.
-}
batch :: IO a -> IO a
#if defined(linux_HOST_OS) || defined(__ANDROID__)
batch a = wait =<< batchthread
where
batchthread = asyncBound $ do
setProcessPriority 0 maxNice
a
#else
batch a = a
#endif
maxNice :: Int
maxNice = 19
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