check-ignore resource pool

Much like check-attr before.

Annex/CheckIgnore.hs

@@ -1,37 +1,57 @@
 {- git check-ignore interface, with handle automatically stored in
  - the Annex monad
  -
- - Copyright 2013 Joey Hess <id@joeyh.name>
+ - Copyright 2013-2020 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
 module Annex.CheckIgnore (
 	checkIgnored,
-	checkIgnoreHandle,
-	checkIgnoreStop
+	checkIgnoreStop,
+	mkConcurrentCheckIgnoreHandle,
 ) where
 
 import Annex.Common
 import qualified Git.CheckIgnore as Git
 import qualified Annex
+import Utility.ResourcePool
+import Types.Concurrency
+import Annex.Concurrent.Utility
 
 checkIgnored :: FilePath -> Annex Bool
-checkIgnored file = go =<< checkIgnoreHandle
-  where
-	go h = liftIO $ Git.checkIgnored h file
+checkIgnored file = withCheckIgnoreHandle $ \h ->
+	liftIO $ Git.checkIgnored h file
 
-checkIgnoreHandle :: Annex Git.CheckIgnoreHandle
-checkIgnoreHandle = maybe startup return =<< Annex.getState Annex.checkignorehandle
+withCheckIgnoreHandle :: (Git.CheckIgnoreHandle -> Annex a) -> Annex a
+withCheckIgnoreHandle a =
+	maybe mkpool go =<< Annex.getState Annex.checkignorehandle
   where
-	startup = do
-		h <- inRepo Git.checkIgnoreStart
-		Annex.changeState $ \s -> s { Annex.checkignorehandle = Just h }
-		return h
+	go p = withResourcePool p start a
+	start = inRepo Git.checkIgnoreStart
+	mkpool = do
+		-- This only runs in non-concurrent code paths;
+		-- a concurrent pool is set up earlier when needed.
+		p <- mkResourcePoolNonConcurrent start
+		Annex.changeState $ \s -> s { Annex.checkignorehandle = Just p }
+		go p
+
+mkConcurrentCheckIgnoreHandle :: Concurrency -> Annex (ResourcePool Git.CheckIgnoreHandle)
+mkConcurrentCheckIgnoreHandle c =
+	Annex.getState Annex.checkignorehandle >>= \case
+		Just p@(ResourcePool {}) -> return p
+		_ -> mkResourcePool =<< liftIO (maxCheckIgnores c)
+
+{- git check-ignore is typically CPU bound, and is not likely to be the main
+ - bottleneck for any command. So limit to the number of CPU cores, maximum,
+ - while respecting the -Jn value.
+ -}
+maxCheckIgnores :: Concurrency -> IO Int
+maxCheckIgnores = concurrencyUpToCpus
 
 checkIgnoreStop :: Annex ()
 checkIgnoreStop = maybe noop stop =<< Annex.getState Annex.checkignorehandle
   where
-	stop h = do
-		liftIO $ Git.checkIgnoreStop h
+	stop p = do
+		liftIO $ freeResourcePool p Git.checkIgnoreStop
 		Annex.changeState $ \s -> s { Annex.checkignorehandle = Nothing }