8237484: Improve module system bootstrap

Reviewed-by: alanb

src/java.base/share/classes/java/lang/Module.java

@@ -132,7 +132,7 @@
         Version version = descriptor.version().orElse(null);
         String vs = Objects.toString(version, null);
         String loc = Objects.toString(uri, null);
-        String[] packages = descriptor.packages().toArray(new String[0]);
+        Object[] packages = descriptor.packages().toArray();
         defineModule0(this, isOpen, vs, loc, packages);
     }
 
@@ -1075,35 +1075,49 @@ public boolean canUse(Class<?> service) {
     {
         boolean isBootLayer = (ModuleLayer.boot() == null);
 
-        int cap = (int)(cf.modules().size() / 0.75f + 1.0f);
+        int numModules = cf.modules().size();
+        int cap = (int)(numModules / 0.75f + 1.0f);
         Map<String, Module> nameToModule = new HashMap<>(cap);
-        Map<String, ClassLoader> nameToLoader = new HashMap<>(cap);
 
-        Set<ClassLoader> loaders = new HashSet<>();
+        // to avoid repeated lookups and reduce iteration overhead, we create
+        // arrays holding correlated information about each module.
+        ResolvedModule[] resolvedModules = new ResolvedModule[numModules];
+        Module[] modules = new Module[numModules];
+        ClassLoader[] classLoaders = new ClassLoader[numModules];
+
+        resolvedModules = cf.modules().toArray(resolvedModules);
+
+        // record that we want to bind the layer to non-boot and non-platform
+        // module loaders as a final step
+        HashSet<ClassLoader> toBindLoaders = new HashSet<>(4);
         boolean hasPlatformModules = false;
 
         // map each module to a class loader
-        for (ResolvedModule resolvedModule : cf.modules()) {
-            String name = resolvedModule.name();
+        ClassLoader pcl = ClassLoaders.platformClassLoader();
+
+        for (int index = 0; index < numModules; index++) {
+            String name = resolvedModules[index].name();
             ClassLoader loader = clf.apply(name);
-            nameToLoader.put(name, loader);
-            if (loader == null || loader == ClassLoaders.platformClassLoader()) {
+
+            if (loader == null || loader == pcl) {
                 if (!(clf instanceof ModuleLoaderMap.Mapper)) {
                     throw new IllegalArgumentException("loader can't be 'null'"
                             + " or the platform class loader");
                 }
                 hasPlatformModules = true;
             } else {
-                loaders.add(loader);
+                toBindLoaders.add(loader);
             }
+
+            classLoaders[index] = loader;
         }
 
         // define each module in the configuration to the VM
-        for (ResolvedModule resolvedModule : cf.modules()) {
-            ModuleReference mref = resolvedModule.reference();
+        for (int index = 0; index < numModules; index++) {
+            ModuleReference mref = resolvedModules[index].reference();
             ModuleDescriptor descriptor = mref.descriptor();
             String name = descriptor.name();
-            ClassLoader loader = nameToLoader.get(name);
+            ClassLoader loader = classLoaders[index];
             Module m;
             if (loader == null && name.equals("java.base")) {
                 // java.base is already defined to the VM
@@ -1113,16 +1127,15 @@ public boolean canUse(Class<?> service) {
                 m = new Module(layer, loader, descriptor, uri);
             }
             nameToModule.put(name, m);
+            modules[index] = m;
         }
 
         // setup readability and exports/opens
-        for (ResolvedModule resolvedModule : cf.modules()) {
+        for (int index = 0; index < numModules; index++) {
+            ResolvedModule resolvedModule = resolvedModules[index];
             ModuleReference mref = resolvedModule.reference();
             ModuleDescriptor descriptor = mref.descriptor();
-
-            String mn = descriptor.name();
-            Module m = nameToModule.get(mn);
-            assert m != null;
+            Module m = modules[index];
 
             // reads
             Set<Module> reads = new HashSet<>();
@@ -1174,16 +1187,15 @@ public boolean canUse(Class<?> service) {
         // if there are modules defined to the boot or platform class loaders
         // then register the modules in the class loader's services catalog
         if (hasPlatformModules) {
-            ClassLoader pcl = ClassLoaders.platformClassLoader();
             ServicesCatalog bootCatalog = BootLoader.getServicesCatalog();
             ServicesCatalog pclCatalog = ServicesCatalog.getServicesCatalog(pcl);
-            for (ResolvedModule resolvedModule : cf.modules()) {
+            for (int index = 0; index < numModules; index++) {
+                ResolvedModule resolvedModule = resolvedModules[index];
                 ModuleReference mref = resolvedModule.reference();
                 ModuleDescriptor descriptor = mref.descriptor();
                 if (!descriptor.provides().isEmpty()) {
-                    String name = descriptor.name();
-                    Module m = nameToModule.get(name);
-                    ClassLoader loader = nameToLoader.get(name);
+                    Module m = modules[index];
+                    ClassLoader loader = classLoaders[index];
                     if (loader == null) {
                         bootCatalog.register(m);
                     } else if (loader == pcl) {
@@ -1194,7 +1206,7 @@ public boolean canUse(Class<?> service) {
         }
 
         // record that there is a layer with modules defined to the class loader
-        for (ClassLoader loader : loaders) {
+        for (ClassLoader loader : toBindLoaders) {
             layer.bindToLoader(loader);
         }
 
@@ -1623,7 +1635,7 @@ private static native void defineModule0(Module module,
                                              boolean isOpen,
                                              String version,
                                              String location,
-                                             String[] pns);
+                                             Object[] pns);
 
     // JVM_AddReadsModule
     private static native void addReads0(Module from, Module to);

src/java.base/share/classes/jdk/internal/module/ModuleBootstrap.java

@@ -140,9 +140,9 @@ public static ModuleFinder limitedFinder() {
      */
     public static ModuleLayer boot() throws Exception {
 
-        // Step 0: Command line options
+        Counters.start();
 
-        long t0 = System.nanoTime();
+        // Step 0: Command line options
 
         ModuleFinder upgradeModulePath = finderFor("jdk.module.upgrade.path");
         ModuleFinder appModulePath = finderFor("jdk.module.path");
@@ -157,15 +157,14 @@ public static ModuleLayer boot() throws Exception {
         if (trace != null && Boolean.parseBoolean(trace))
             traceOutput = System.out;
 
+        Counters.add("jdk.module.boot.0.commandLineTime");
 
         // Step 1: The observable system modules, either all system modules
         // or the system modules pre-generated for the initial module (the
         // initial module may be the unnamed module). If the system modules
         // are pre-generated for the initial module then resolution can be
         // skipped.
 
-        long t1 = System.nanoTime();
-
         SystemModules systemModules = null;
         ModuleFinder systemModuleFinder;
 
@@ -215,16 +214,13 @@ public static ModuleLayer boot() throws Exception {
             archivedModuleGraph = null;
         }
 
-        Counters.add("jdk.module.boot.1.systemModulesTime", t1);
-
+        Counters.add("jdk.module.boot.1.systemModulesTime");
 
         // Step 2: Define and load java.base. This patches all classes loaded
         // to date so that they are members of java.base. Once java.base is
         // loaded then resources in java.base are available for error messages
         // needed from here on.
 
-        long t2 = System.nanoTime();
-
         ModuleReference base = systemModuleFinder.find(JAVA_BASE).orElse(null);
         if (base == null)
             throw new InternalError(JAVA_BASE + " not found");
@@ -234,9 +230,6 @@ public static ModuleLayer boot() throws Exception {
         BootLoader.loadModule(base);
         Modules.defineModule(null, base.descriptor(), baseUri);
 
-        Counters.add("jdk.module.boot.2.defineBaseTime", t2);
-
-
         // Step 2a: Scan all modules when --validate-modules specified
 
         if (getAndRemoveProperty("jdk.module.validation") != null) {
@@ -246,12 +239,11 @@ public static ModuleLayer boot() throws Exception {
             }
         }
 
+        Counters.add("jdk.module.boot.2.defineBaseTime");
 
         // Step 3: If resolution is needed then create the module finder and
         // the set of root modules to resolve.
 
-        long t3 = System.nanoTime();
-
         ModuleFinder savedModuleFinder = null;
         ModuleFinder finder;
         Set<String> roots;
@@ -341,15 +333,13 @@ public static ModuleLayer boot() throws Exception {
             roots = null;
         }
 
-        Counters.add("jdk.module.boot.3.optionsAndRootsTime", t3);
+        Counters.add("jdk.module.boot.3.optionsAndRootsTime");
 
         // Step 4: Resolve the root modules, with service binding, to create
         // the configuration for the boot layer. If resolution is not needed
         // then create the configuration for the boot layer from the
         // readability graph created at link time.
 
-        long t4 = System.nanoTime();
-
         Configuration cf;
         if (needResolution) {
             cf = Modules.newBootLayerConfiguration(finder, roots, traceOutput);
@@ -370,8 +360,7 @@ public static ModuleLayer boot() throws Exception {
                     .forEach(mn -> warnUnknownModule(PATCH_MODULE, mn));
         }
 
-        Counters.add("jdk.module.boot.4.resolveTime", t4);
-
+        Counters.add("jdk.module.boot.4.resolveTime");
 
         // Step 5: Map the modules in the configuration to class loaders.
         // The static configuration provides the mapping of standard and JDK
@@ -380,8 +369,6 @@ public static ModuleLayer boot() throws Exception {
         // application module path) are defined to the application class
         // loader.
 
-        long t5 = System.nanoTime();
-
         // mapping of modules to class loaders
         Function<String, ClassLoader> clf = ModuleLoaderMap.mappingFunction(cf);
 
@@ -409,16 +396,12 @@ public static ModuleLayer boot() throws Exception {
 
         // load/register the modules with the built-in class loaders
         loadModules(cf, clf);
-
-        Counters.add("jdk.module.boot.5.loadModulesTime", t5);
-
+        Counters.add("jdk.module.boot.5.loadModulesTime");
 
         // Step 6: Define all modules to the VM
 
-        long t6 = System.nanoTime();
         ModuleLayer bootLayer = ModuleLayer.empty().defineModules(cf, clf);
-        Counters.add("jdk.module.boot.6.layerCreateTime", t6);
-
+        Counters.add("jdk.module.boot.6.layerCreateTime");
 
         // Step 7: Miscellaneous
 
@@ -428,7 +411,6 @@ public static ModuleLayer boot() throws Exception {
         }
 
         // --add-reads, --add-exports/--add-opens, and --illegal-access
-        long t7 = System.nanoTime();
         addExtraReads(bootLayer);
         boolean extraExportsOrOpens = addExtraExportsAndOpens(bootLayer);
 
@@ -446,7 +428,7 @@ public static ModuleLayer boot() throws Exception {
                          exportedPackagesToOpen,
                          bootLayer,
                          extraExportsOrOpens);
-        Counters.add("jdk.module.boot.7.adjustModulesTime", t7);
+        Counters.add("jdk.module.boot.7.adjustModulesTime");
 
         // save module finders for later use
         if (savedModuleFinder != null) {
@@ -468,8 +450,7 @@ public static ModuleLayer boot() throws Exception {
         }
 
         // total time to initialize
-        Counters.add("jdk.module.boot.totalTime", t0);
-        Counters.publish();
+        Counters.publish("jdk.module.boot.totalTime");
 
         return bootLayer;
     }
@@ -1030,6 +1011,9 @@ static String option(String prefix) {
         private static final boolean PUBLISH_COUNTERS;
         private static final boolean PRINT_COUNTERS;
         private static Map<String, Long> counters;
+        private static long startTime;
+        private static long previousTime;
+
         static {
             String s = System.getProperty("jdk.module.boot.usePerfData");
             if (s == null) {
@@ -1043,27 +1027,44 @@ static String option(String prefix) {
         }
 
         /**
-         * Add a counter
+         * Start counting time.
+         */
+        static void start() {
+            if (PUBLISH_COUNTERS) {
+                startTime = previousTime = System.nanoTime();
+            }
+        }
+
+        /**
+         * Add a counter - storing the time difference between now and the
+         * previous add or the start.
          */
-        static void add(String name, long start) {
-            if (PUBLISH_COUNTERS || PRINT_COUNTERS) {
-                counters.put(name, (System.nanoTime() - start));
+        static void add(String name) {
+            if (PUBLISH_COUNTERS) {
+                long current = System.nanoTime();
+                long elapsed = current - previousTime;
+                previousTime = current;
+                counters.put(name, elapsed);
             }
         }
 
         /**
          * Publish the counters to the instrumentation buffer or stdout.
          */
-        static void publish() {
-            if (PUBLISH_COUNTERS || PRINT_COUNTERS) {
+        static void publish(String totalTimeName) {
+            if (PUBLISH_COUNTERS) {
+                long currentTime = System.nanoTime();
                 for (Map.Entry<String, Long> e : counters.entrySet()) {
                     String name = e.getKey();
                     long value = e.getValue();
-                    if (PUBLISH_COUNTERS)
-                        PerfCounter.newPerfCounter(name).set(value);
+                    PerfCounter.newPerfCounter(name).set(value);
                     if (PRINT_COUNTERS)
                         System.out.println(name + " = " + value);
                 }
+                long elapsedTotal = currentTime - startTime;
+                PerfCounter.newPerfCounter(totalTimeName).set(elapsedTotal);
+                if (PRINT_COUNTERS)
+                    System.out.println(totalTimeName + " = " + elapsedTotal);
             }
         }
     }