new improved benchmark command that can benchmark anything git-annex does

Benchmark.hs

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+{- git-annex benchmark infrastructure
+ -
+ - Copyright 2019 Joey Hess <id@joeyh.name>
+ -
+ - Licensed under the GNU AGPL version 3 or higher.
+ -}
+
+module Benchmark where
+
+import Common
+import Types.Benchmark
+import Types.Command
+import CmdLine.Action
+import CmdLine
+import CmdLine.GitAnnex.Options
+import qualified Annex
+import qualified Annex.Branch
+import Annex.Action
+
+import qualified Options.Applicative as O
+
+{- Given a list of all git-annex Commands, and the user's input,
+ - generates an IO action to benchmark that runs the specified
+ - commands. -}
+mkGenerator :: MkBenchmarkGenerator
+mkGenerator cmds userinput = do
+	-- Get the git-annex branch updated, to avoid the overhead of doing
+	-- so skewing the runtime of the first action that will be
+	-- benchmarked.
+	Annex.Branch.commit "benchmarking"
+	Annex.Branch.update
+	l <- mapM parsesubcommand $ split [";"] userinput
+	return $ do
+		forM_ l $ \(cmd, seek, st) ->
+			-- The cmd is run for benchmarking without startup or
+			-- shutdown actions.
+			Annex.eval st $ performCommandAction cmd seek noop
+		-- Since the cmd will be run many times, some zombie
+		-- processes that normally only occur once per command
+		-- will build up; reap them.
+		reapZombies
+  where
+	-- Simplified versio of CmdLine.dispatch, without support for fuzzy
+	-- matching or out-of-repo commands.
+	parsesubcommand ps = do
+		(cmd, seek, globalconfig) <- liftIO $ O.handleParseResult $
+			parseCmd "git-annex" "benchmarking" gitAnnexGlobalOptions ps cmds cmdparser
+		-- Make an entirely separate Annex state for each subcommand,
+		-- and prepare it to run the cmd.
+		st <- liftIO . Annex.new =<< Annex.getState Annex.repo
+		((), st') <- liftIO $ Annex.run st $
+			prepRunCommand cmd globalconfig
+		return (cmd, seek, st')