Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: 5fab2238 by Wolfgang Jeltsch at 2026-05-12T21:24:27+03:00 Introduce a cache of home module name providers This contribution introduces to the module graph a cache that maps home module names to sets of units providing them and changes the finder to use that cache. This is a performance optimization, especially for multi-home-unit builds. The particular changes are as follows: * In `GHC.Unit.Module.Graph`, `ModuleGraph` is extended with a new field `mg_home_module_name_providers_map`, exposed as `mgHomeModuleNameProvidersMap`. This is a cache that assigns to each home module name the set of IDs of home units that define it. Operations that construct module graphs are updated such that this cache stays synchronized. * In `GHC.Unit.Finder`, `findImportedModule` is changed to pull `mgHomeModuleNameProvidersMap` from `hsc_mod_graph` and pass it to `findImportedModuleNoHsc`, which now does not search home units in arbitrary order but prioritizes those units that the cache mentions as potential providers of the requested module. In addition, this contribution adds variants of the two multi-component compiler performance tests that use 100 units instead of 20, because with just 20 units the benefits from caching of home module name providers are still negligible. The following table shows the total time needed for running both multi-component tests before and after this contribution and with different numbers of units: | # of units | Before | After | |-----------:|-------:|------:| | 20 | 0:12 | 0:12 | | 100 | 0:47 | 0:42 | | 200 | 3:05 | 2:08 | Note that there seems to be a general overhead of 12 seconds that is not attributable to the actual tests, so that the real running times should be 12 seconds smaller than shown above. Resolves #27055. Metric Decrease: MultiComponentModules MultiComponentModulesRecomp Co-authored-by: Matthew Pickering <matthewtpickering@gmail.com> Co-authored-by: Fendor <fendor@posteo.de> - - - - - 6 changed files: - + changelog.d/more-efficient-home-unit-imports-finding - compiler/GHC/Unit/Finder.hs - compiler/GHC/Unit/Module/Graph.hs - testsuite/tests/perf/compiler/Makefile - testsuite/tests/perf/compiler/all.T - testsuite/tests/perf/compiler/genMultiComp.py Changes: ===================================== changelog.d/more-efficient-home-unit-imports-finding ===================================== @@ -0,0 +1,15 @@ +section: compiler +synopsis: Introduce a cache of home module name providers +issues: #27055 +mrs: !15888 +description: { + This contribution optimizes the algorithm for finding out which home + unit provides the module that a certain import declaration refers + to. The previous approach has been to simply search all home units + in no particular order. This change introduces a cache that allows + for efficiently determining those complete home units that provide a + certain module name and changes the module-finding algorithm such + that it searches these units before the other home units. This leads + to significant performance improvements in situations where there + are lots of home units. +} ===================================== compiler/GHC/Unit/Finder.hs ===================================== @@ -44,6 +44,11 @@ import GHC.Data.OsPath import GHC.Unit.Env import GHC.Unit.Types import GHC.Unit.Module +import GHC.Unit.Module.Graph + ( + HomeModuleNameProvidersMap, + mgHomeModuleNameProvidersMap + ) import GHC.Unit.Home import GHC.Unit.Home.Graph (UnitEnvGraph) import qualified GHC.Unit.Home.Graph as HUG @@ -72,7 +77,8 @@ import GHC.Driver.Config.Finder import GHC.Types.Unique.Set import qualified Data.List as L(sort) import Data.List.NonEmpty ( NonEmpty (..) ) -import qualified Data.Set as Set (toList) +import Data.Set (Set) +import qualified Data.Set as Set (empty, intersection, difference, null, toList) import qualified System.Directory as SD import qualified System.OsPath as OsPath import qualified Data.List.NonEmpty as NE @@ -177,12 +183,13 @@ getDirHash dir = do findImportedModule :: HscEnv -> ModuleName -> PkgQual -> IO FindResult findImportedModule hsc_env mod pkg_qual = - let fc = hsc_FC hsc_env - mhome_unit = hsc_home_unit_maybe hsc_env - dflags = hsc_dflags hsc_env - fopts = initFinderOpts dflags + let fc = hsc_FC hsc_env + mb_home_unit = hsc_home_unit_maybe hsc_env + dflags = hsc_dflags hsc_env + fopts = initFinderOpts dflags in do - findImportedModuleNoHsc fc fopts (hsc_unit_env hsc_env) mhome_unit mod pkg_qual + let home_module_name_providers_map = mgHomeModuleNameProvidersMap (hsc_mod_graph hsc_env) + findImportedModuleNoHsc fc fopts (hsc_unit_env hsc_env) home_module_name_providers_map mb_home_unit mod pkg_qual findImportedModuleWithIsBoot :: HscEnv -> ModuleName -> IsBootInterface -> PkgQual -> IO FindResult findImportedModuleWithIsBoot hsc_env mod is_boot pkg_qual = do @@ -195,55 +202,126 @@ findImportedModuleNoHsc :: FinderCache -> FinderOpts -> UnitEnv + -> HomeModuleNameProvidersMap -> Maybe HomeUnit -> ModuleName -> PkgQual -> IO FindResult -findImportedModuleNoHsc fc fopts ue mhome_unit mod_name mb_pkg = +findImportedModuleNoHsc fc fopts ue home_module_name_providers_map mb_home_unit mod_name mb_pkg = case mb_pkg of NoPkgQual -> unqual_import - ThisPkg uid | (homeUnitId <$> mhome_unit) == Just uid -> home_import + ThisPkg uid | (homeUnitId <$> mb_home_unit) == Just uid -> home_import | Just os <- lookup uid other_fopts -> home_pkg_import (uid, os) - | otherwise -> pprPanic "findImportModule" (ppr mod_name $$ ppr mb_pkg $$ ppr (homeUnitId <$> mhome_unit) $$ ppr uid $$ ppr (map fst all_opts)) + | otherwise -> pprPanic "findImportModule" (ppr mod_name $$ ppr mb_pkg $$ ppr (homeUnitId <$> mb_home_unit) $$ ppr uid $$ ppr (map fst all_opts)) OtherPkg _ -> pkg_import where - all_opts = case mhome_unit of - Nothing -> other_fopts - Just home_unit -> (homeUnitId home_unit, fopts) : other_fopts + mb_home_unit_id :: Maybe UnitId + mb_home_unit_id = homeUnitId <$> mb_home_unit - home_import = case mhome_unit of - Just home_unit -> findHomeModule fc fopts home_unit mod_name - Nothing -> pure $ NoPackage (panic "findImportedModule: no home-unit") + all_opts :: [(UnitId, FinderOpts)] + all_opts = case mb_home_unit_id of + Nothing -> other_fopts + Just home_unit_id -> (home_unit_id, fopts) : other_fopts + home_import :: IO FindResult + home_import = case mb_home_unit of + Just home_unit -> findHomeModule fc fopts home_unit mod_name + Nothing -> pure $ + NoPackage (panic "findImportedModule: no home-unit") + home_pkg_import :: (UnitId, FinderOpts) -> IO FindResult home_pkg_import (uid, opts) - -- If the module is reexported, then look for it as if it was from the perspective - -- of that package which reexports it. - | Just real_mod_name <- lookupUniqMap (finder_reexportedModules opts) mod_name = - findImportedModuleNoHsc fc opts ue (Just $ DefiniteHomeUnit uid Nothing) real_mod_name NoPkgQual - | elementOfUniqSet mod_name (finder_hiddenModules opts) = - return (mkHomeHidden uid) - | otherwise = - findHomePackageModule fc opts uid mod_name - - -- Do not be smart and change this to `foldr orIfNotFound home_import hs` as - -- that is not the same!! home_import is first because we need to look within ourselves - -- first before looking at the packages in order. - any_home_import = foldr1 orIfNotFound (home_import:| map home_pkg_import other_fopts) - - pkg_import = findExposedPackageModule fc fopts units mod_name mb_pkg - - unqual_import = any_home_import - `orIfNotFound` - findExposedPackageModule fc fopts units mod_name NoPkgQual - - units = case mhome_unit of - Nothing -> ue_homeUnitState ue - Just home_unit -> HUG.homeUnitEnv_units $ ue_findHomeUnitEnv (homeUnitId home_unit) ue - hpt_deps :: [UnitId] - hpt_deps = Set.toList (homeUnitDepends units) - other_fopts = map (\uid -> (uid, initFinderOpts (homeUnitEnv_dflags (ue_findHomeUnitEnv uid ue)))) hpt_deps + -- If the module is reexported, then look for it as if it was from the + -- perspective of that package which reexports it. + | Just real_mod_name + <- lookupUniqMap (finder_reexportedModules opts) mod_name + = findImportedModuleNoHsc fc opts ue home_module_name_providers_map + (Just $ DefiniteHomeUnit uid Nothing) + real_mod_name + NoPkgQual + | elementOfUniqSet mod_name (finder_hiddenModules opts) + = return (mkHomeHidden uid) + | otherwise + = findHomePackageModule fc opts uid mod_name + + any_home_import :: IO FindResult + any_home_import = foldr1 orIfNotFound $ + home_import :| map home_pkg_import other_fopts + -- Do not try to be smart and change this to `foldr orIfNotFound home_import + -- (map home_pkg_import other_fopts)`, as that would not be the same. + -- `home_import` is first because we need to first look within the current + -- unit before looking at the other units in order. + + pkg_import :: IO FindResult + pkg_import = findExposedPackageModule fc fopts unit_state mod_name mb_pkg + + unqual_import :: IO FindResult + unqual_import + = any_home_import + `orIfNotFound` + findExposedPackageModule fc fopts unit_state mod_name NoPkgQual + + unit_state :: UnitState + unit_state = case mb_home_unit_id of + Nothing -> ue_homeUnitState ue + Just home_unit_id -> HUG.homeUnitEnv_units $ + ue_findHomeUnitEnv home_unit_id ue + + home_unit_deps :: Set UnitId + home_unit_deps = homeUnitDepends unit_state + + ranked_home_unit_deps :: [UnitId] + ranked_home_unit_deps = rankedHomeUnitDeps home_module_name_providers_map + mod_name + home_unit_deps + + other_fopts :: [(UnitId, FinderOpts)] + other_fopts + = [ + (uid, opts) | + uid <- ranked_home_unit_deps, + let opts = initFinderOpts $ + homeUnitEnv_dflags (ue_findHomeUnitEnv uid ue) + ] + +-- | Yields the unit IDs from the given set as a list with those that refer to +-- providers of the given home module name coming first. This is to prioritize +-- such providers during module finding. +rankedHomeUnitDeps :: HomeModuleNameProvidersMap + -> ModuleName + -> Set UnitId + -> [UnitId] +rankedHomeUnitDeps _ _ home_unit_deps | Set.null home_unit_deps + = [] +-- The special handling of the situation where the dependency set is empty does +-- not change the result, but it avoids triggering evaluation of the module +-- graph. This is particularly important in one-shot mode, where the module +-- graph is not needed. Computing it nevertheless would result in a, possibly +-- dramatic, increase of memory usage. Worse, GHC would erroneously look for the +-- sources of modules, which would, for example, cause test `boot1` to fail with +-- the following error message: +-- +-- B.hs:3:1: error: [GHC-87110] +-- Could not find module ‘A’. +-- Use -v to see a list of the files searched for. +-- | +-- 3 | import {-# source #-} A +-- | ^^^^^^^^^^^^^^^^^^^^^^^ +rankedHomeUnitDeps home_module_name_providers_map mod_name home_unit_deps + = Set.toList cached_deps ++ Set.toList uncached_deps + where + + cached_providers :: Set UnitId + cached_providers = lookupWithDefaultUniqMap home_module_name_providers_map + Set.empty + mod_name + + cached_deps :: Set UnitId + cached_deps = Set.intersection home_unit_deps cached_providers + + uncached_deps :: Set UnitId + uncached_deps = Set.difference home_unit_deps cached_providers -- | Locate a plugin module requested by the user, for a compiler -- plugin. This consults the same set of exposed packages as @@ -261,15 +339,15 @@ findPluginModule :: HscEnv -> ModuleName -> IO FindResult findPluginModule hsc_env mod_name = do let fc = hsc_FC hsc_env let units = hsc_units hsc_env - let mhome_unit = hsc_home_unit_maybe hsc_env - findPluginModuleNoHsc fc (initFinderOpts (hsc_dflags hsc_env)) units mhome_unit mod_name + let mb_home_unit = hsc_home_unit_maybe hsc_env + findPluginModuleNoHsc fc (initFinderOpts (hsc_dflags hsc_env)) units mb_home_unit mod_name -- | A version of findExactModule which takes the exact parts of the HscEnv it needs -- directly. findExactModuleNoHsc :: FinderCache -> FinderOpts -> UnitEnvGraph FinderOpts -> UnitState -> Maybe HomeUnit -> InstalledModule -> IsBootInterface -> IO InstalledFindResult -findExactModuleNoHsc fc fopts other_fopts unit_state mhome_unit mod is_boot = do - res <- case mhome_unit of +findExactModuleNoHsc fc fopts other_fopts unit_state mb_home_unit mod is_boot = do + res <- case mb_home_unit of Just home_unit | isHomeInstalledModule home_unit mod -> findInstalledHomeModule fc fopts (homeUnitId home_unit) (moduleName mod) ===================================== compiler/GHC/Unit/Module/Graph.hs ===================================== @@ -67,6 +67,8 @@ module GHC.Unit.Module.Graph , mgLookupModule , mgLookupModuleName , mgHasHoles + , HomeModuleNameProvidersMap + , mgHomeModuleNameProvidersMap , showModMsg -- ** Reachability queries @@ -156,10 +158,12 @@ import GHC.Unit.Module.ModIface import GHC.Utils.Misc ( partitionWith ) import System.FilePath +import Data.Set (Set) +import qualified Data.Set as Set +import Data.Map (Map) import qualified Data.Map as Map import GHC.Types.Unique.DSet -import qualified Data.Set as Set -import Data.Set (Set) +import GHC.Types.Unique.Map (UniqMap, emptyUniqMap, listToUniqMap_C) import GHC.Unit.Module import GHC.Unit.Module.ModNodeKey import GHC.Unit.Module.Stage @@ -202,14 +206,32 @@ data ModuleGraph = ModuleGraph -- Cached computation, whether any of the ModuleGraphNode are isHoleModule, -- This is only used for a hack in GHC.Iface.Load to do with backpack, please -- remove this at the earliest opportunity. + , mg_home_module_name_providers_map :: HomeModuleNameProvidersMap + -- ^ For each module name, which home units provide it. } +type HomeModuleNameProvidersMap = UniqMap ModuleName (Set UnitId) + +mkHomeModuleNameProvidersMap :: [ModuleGraphNode] -> HomeModuleNameProvidersMap +mkHomeModuleNameProvidersMap nodes + = listToUniqMap_C Set.union $ + [ + (moduleName, Set.singleton unitID) | + ModuleNode _ moduleNodeInfo <- nodes, + let moduleName = moduleNodeInfoModuleName moduleNodeInfo, + let unitID = moduleNodeInfoUnitId moduleNodeInfo + ] + +mgHomeModuleNameProvidersMap :: ModuleGraph -> HomeModuleNameProvidersMap +mgHomeModuleNameProvidersMap = mg_home_module_name_providers_map + -- | Why do we ever need to construct empty graphs? Is it because of one shot mode? emptyMG :: ModuleGraph emptyMG = ModuleGraph [] (graphReachability emptyGraph, const Nothing) (graphReachability emptyGraph, const Nothing) (graphReachability emptyGraph, const Nothing) False + emptyUniqMap -- | Construct a module graph. This function should be the only entry point for -- building a 'ModuleGraph', since it is supposed to be built once and never modified. @@ -308,7 +330,7 @@ checkModuleGraph ModuleGraph{..} = where duplicate_errs = rights (Map.elems node_types) - node_types :: Map.Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) + node_types :: Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) node_types = Map.fromListWithKey go [ (mkNodeKey n, Left (moduleNodeType n)) | n <- mg_mss ] where -- Multiple nodes with the same key are not allowed. @@ -319,7 +341,7 @@ checkModuleGraph ModuleGraph{..} = -- | Check that all dependencies in the graph are present in the node_types map. -- This is a helper function used by checkModuleGraph. -checkAllDependenciesInGraph :: Map.Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) +checkAllDependenciesInGraph :: Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) -> ModuleGraphNode -> Maybe ModuleGraphInvariantError checkAllDependenciesInGraph node_types node = @@ -334,7 +356,7 @@ checkAllDependenciesInGraph node_types node = -- | Check if for the fixed module node invariant: -- -- Fixed nodes can only depend on other fixed nodes. -checkFixedModuleInvariant :: Map.Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) +checkFixedModuleInvariant :: Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) -> ModuleGraphNode -> Maybe ModuleGraphInvariantError checkFixedModuleInvariant node_types node = case node of @@ -484,13 +506,17 @@ isEmptyMG = null . mg_mss -- To preserve invariants, 'f' can't change the isBoot status. mapMG :: (ModSummary -> ModSummary) -> ModuleGraph -> ModuleGraph mapMG f mg@ModuleGraph{..} = mg - { mg_mss = flip fmap mg_mss $ \case - InstantiationNode uid iuid -> InstantiationNode uid iuid - LinkNode uid nks -> LinkNode uid nks - ModuleNode deps (ModuleNodeFixed key loc) -> ModuleNode deps (ModuleNodeFixed key loc) - ModuleNode deps (ModuleNodeCompile ms) -> ModuleNode deps (ModuleNodeCompile (f ms)) - UnitNode deps uid -> UnitNode deps uid + { mg_mss = new_mss + , mg_home_module_name_providers_map = mkHomeModuleNameProvidersMap new_mss } + where + new_mss = + flip fmap mg_mss $ \case + InstantiationNode uid iuid -> InstantiationNode uid iuid + LinkNode uid nks -> LinkNode uid nks + ModuleNode deps (ModuleNodeFixed key loc) -> ModuleNode deps (ModuleNodeFixed key loc) + ModuleNode deps (ModuleNodeCompile ms) -> ModuleNode deps (ModuleNodeCompile (f ms)) + UnitNode deps uid -> UnitNode deps uid -- | Map a function 'f' over all the 'ModSummaries', in 'IO'. -- To preserve invariants, 'f' can't change the isBoot status. @@ -856,7 +882,7 @@ moduleNodeInfoBootString mn@(ModuleNodeFixed {}) = -- described in the export list haddocks. -------------------------------------------------------------------------------- -newtype NodeMap a = NodeMap { unNodeMap :: Map.Map NodeKey a } +newtype NodeMap a = NodeMap { unNodeMap :: Map NodeKey a } deriving (Functor, Traversable, Foldable) -- | Transitive dependencies, including SOURCE edges @@ -932,7 +958,7 @@ moduleGraphNodesZero summaries = lookup_key :: ZeroScopeKey -> Maybe Int lookup_key = fmap zeroSummaryNodeKey . lookup_node - node_map :: Map.Map ZeroScopeKey ZeroSummaryNode + node_map :: Map ZeroScopeKey ZeroSummaryNode node_map = Map.fromList [ (s, node) | node <- nodes @@ -1031,7 +1057,7 @@ moduleGraphNodesStages summaries = lookup_key :: (NodeKey, ModuleStage) -> Maybe Int lookup_key = fmap stageSummaryNodeKey . lookup_node - node_map :: Map.Map (NodeKey, ModuleStage) StageSummaryNode + node_map :: Map (NodeKey, ModuleStage) StageSummaryNode node_map = Map.fromList [ (s, node) | node <- nodes @@ -1049,10 +1075,13 @@ moduleGraphNodesStages summaries = extendMG :: ModuleGraph -> ModuleGraphNode -> ModuleGraph extendMG ModuleGraph{..} node = ModuleGraph - { mg_mss = node : mg_mss - , mg_graph = mkTransDeps (node : mg_mss) - , mg_loop_graph = mkTransLoopDeps (node : mg_mss) - , mg_zero_graph = mkTransZeroDeps (node : mg_mss) + { mg_mss = new_mss + , mg_graph = mkTransDeps new_mss + , mg_loop_graph = mkTransLoopDeps new_mss + , mg_zero_graph = mkTransZeroDeps new_mss , mg_has_holes = mg_has_holes || maybe False isHsigFile (moduleNodeInfoHscSource =<< mgNodeIsModule node) + , mg_home_module_name_providers_map = mkHomeModuleNameProvidersMap new_mss } + where + new_mss = node : mg_mss ===================================== testsuite/tests/perf/compiler/Makefile ===================================== @@ -31,7 +31,11 @@ MultiModulesDefsWithCore: ./genMultiLayerModulesCore MultiComponentModulesRecomp: - '$(PYTHON)' genMultiComp.py + '$(PYTHON)' genMultiComp.py 20 20 + TEST_HC='$(TEST_HC)' TEST_HC_OPTS='$(TEST_HC_OPTS)' ./run + +MultiComponentModulesRecomp100: + '$(PYTHON)' genMultiComp.py 100 20 TEST_HC='$(TEST_HC)' TEST_HC_OPTS='$(TEST_HC_OPTS)' ./run MultiLayerModulesTH_Make_Prep: ===================================== testsuite/tests/perf/compiler/all.T ===================================== @@ -507,13 +507,31 @@ test('MultiComponentModulesRecomp', test('MultiComponentModules', [ collect_compiler_runtime(2), - pre_cmd('$PYTHON ./genMultiComp.py'), + pre_cmd('$PYTHON ./genMultiComp.py 20 20'), extra_files(['genMultiComp.py']), compile_timeout_multiplier(5) ], multiunit_compile, [['unitp%d' % n for n in range(20)], '-fno-code -fwrite-interface -v0']) +test('MultiComponentModulesRecomp100', + [ collect_compiler_runtime(2), + pre_cmd('$MAKE -s --no-print-directory MultiComponentModulesRecomp100'), + extra_files(['genMultiComp.py']), + compile_timeout_multiplier(5) + ], + multiunit_compile, + [['unitp%d' % n for n in range(100)], '-fno-code -fwrite-interface -v0']) + +test('MultiComponentModules100', + [ collect_compiler_runtime(2), + pre_cmd('$PYTHON ./genMultiComp.py 100 20'), + extra_files(['genMultiComp.py']), + compile_timeout_multiplier(5) + ], + multiunit_compile, + [['unitp%d' % n for n in range(100)], '-fno-code -fwrite-interface -v0']) + test('ManyConstructors', [ collect_compiler_stats('bytes allocated',2), pre_cmd('./genManyConstructors'), ===================================== testsuite/tests/perf/compiler/genMultiComp.py ===================================== @@ -7,11 +7,12 @@ # * A number of modules names Mod_<pid>_<mid>, each module imports all the top # modules beneath it, and all the modules in the current unit beneath it. +import sys import os import stat -modules_per = 20 -packages = 20 +packages = int(sys.argv[1]) +modules_per = int(sys.argv[2]) total = modules_per * packages def unit_dir(p): View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/5fab22387a66657e5e19f1ba490f09af... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/5fab22387a66657e5e19f1ba490f09af... 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