Reduce service isolate startup time from ~80ms to ~30ms

runtime/bin/vmservice_impl.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/vmservice_impl.h"
 
 #include "include/dart_api.h"
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
@@ skipping 68 matching lines @@
     return NULL;
   }
   static ResourcesEntry* ResourcesTable() {
     return &__service_bin_resources_[0];
   }
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(Resources);
 };
 
+
+void TriggerResourceLoad(Dart_NativeArguments args) {
+  Dart_Handle library = Dart_RootLibrary();
+  ASSERT(!Dart_IsError(library));
+  Dart_Handle result = VmService::LoadResources(library);
+  ASSERT(!Dart_IsError(result));
+}
+
+
+struct VmServiceIONativeEntry {
+  const char* name;
+  int num_arguments;
+  Dart_NativeFunction function;
+};
+
+
+static VmServiceIONativeEntry _VmServiceIONativeEntries[] = {
+  {"VMServiceIO_TriggerResourceLoad", 0, TriggerResourceLoad},

[siva, 2014/09/09 00:40:58]

in resources.dart triggerResourceLoad is not declared as a static
function but here you have 0 arguments for it, how will this
get resolved correctly?

void _triggerResourceLoad() native "VMServiceIO_TriggerResourceLoad";

+};
+
+
+static Dart_NativeFunction VmServiceIONativeResolver(Dart_Handle name,
+                                                     int num_arguments,
+                                                     bool* auto_setup_scope) {
+  const char* function_name = NULL;
+  Dart_Handle result = Dart_StringToCString(name, &function_name);
+  ASSERT(!Dart_IsError(result));
+  ASSERT(function_name != NULL);
+  *auto_setup_scope = true;
+  intptr_t n =
+      sizeof(_VmServiceIONativeEntries) / sizeof(_VmServiceIONativeEntries[0]);
+  for (intptr_t i = 0; i < n; i++) {
+    VmServiceIONativeEntry entry = _VmServiceIONativeEntries[i];
+    if ((strcmp(function_name, entry.name) == 0) &&
+        (num_arguments == entry.num_arguments)) {
+      return entry.function;
+    }
+  }
+  return NULL;
+}
+
+
 const char* VmService::error_msg_ = NULL;
 
 bool VmService::Start(const char *server_ip, intptr_t server_port) {
   bool r = _Start(server_ip, server_port);
   if (!r) {
     return r;
   }
   // Start processing messages in a new thread.
   Thread::Start(ThreadMain, static_cast<uword>(NULL));
   return true;
 }
 
 
 bool VmService::_Start(const char *server_ip, intptr_t server_port) {
   ASSERT(Dart_CurrentIsolate() == NULL);
   Dart_Isolate isolate = Dart_GetServiceIsolate(NULL);
   if (isolate == NULL) {
-    error_msg_ = "Internal error.";
+    error_msg_ = "Dart_GetServiceIsolate failed.";
     return false;
   }
   Dart_EnterIsolate(isolate);
   Dart_EnterScope();
   // Install our own library tag handler.
   Dart_SetLibraryTagHandler(LibraryTagHandler);
   Dart_Handle result;
-  Dart_Handle library = LoadScript(kVMServiceIOLibraryScriptResourceName);
-  // Expect a library.
-  ASSERT(library != Dart_Null());
-  SHUTDOWN_ON_ERROR(library);
-  result = Dart_FinalizeLoading(false);
-  ASSERT(!Dart_IsError(result));
+  Dart_Handle library;
+  {
+    library = LoadScript(kVMServiceIOLibraryScriptResourceName);
+    // Expect a library.
+    ASSERT(library != Dart_Null());
+    SHUTDOWN_ON_ERROR(library);
+    result = Dart_FinalizeLoading(false);
+    ASSERT(!Dart_IsError(result));
+  }

[siva, 2014/09/09 00:40:58]

Why is this is a special scope?

[Cutch, 2014/09/10 15:11:23]

I was using scoped timers. Removing extra scopes.

   Dart_ExitScope();
   Dart_ExitIsolate();
   bool retval = Dart_IsolateMakeRunnable(isolate);
   if (!retval) {
     Dart_EnterIsolate(isolate);
     Dart_ShutdownIsolate();
     error_msg_ = "Invalid isolate state - Unable to make it runnable.";
     return false;
   }
 
-  Dart_EnterIsolate(isolate);
-  Dart_EnterScope();
-  library = Dart_RootLibrary();
-  // Set requested TCP port.
-  DartUtils::SetStringField(library, "_ip", server_ip);
-  // If we have a port specified, start the server immediately.
-  bool auto_start = server_port >= 0;
-  if (server_port < 0) {
-    // Adjust server_port to port 0 which will result in the first available
-    // port when the HTTP server is started.
-    server_port = 0;
+  {
+    Dart_EnterIsolate(isolate);
+    Dart_EnterScope();
+    library = Dart_RootLibrary();
+    result = Dart_SetNativeResolver(library, VmServiceIONativeResolver, NULL);
+    ASSERT(!Dart_IsError(result));
+    // Set requested TCP port.
+    DartUtils::SetStringField(library, "_ip", server_ip);
+    // If we have a port specified, start the server immediately.
+    bool auto_start = server_port >= 0;
+    if (server_port < 0) {
+      // Adjust server_port to port 0 which will result in the first available
+      // port when the HTTP server is started.
+      server_port = 0;
+    }
+    // Set initial state.
+    DartUtils::SetIntegerField(library, "_port", server_port);
+    Dart_SetField(library,
+                  DartUtils::NewString("_autoStart"),
+                  Dart_NewBoolean(auto_start));
+    // We cannot register for signals on windows.
+  #if defined(TARGET_OS_WINDOWS)
+    const bool is_windows = true;
+  #else
+    const bool is_windows = false;
+  #endif
+    Dart_SetField(library,
+                  DartUtils::NewString("_isWindows"),
+                  Dart_NewBoolean(is_windows));

[siva, 2014/09/09 00:40:58]

Can write this:
#if defined(TARGET_OS_WINDOWS)
Dart_Handle is_windows = Dart_True();
#else
Dart_Handle is_windows = Dart_False();
#endif

Dart_SetField(...., is_windows);

[Cutch, 2014/09/10 15:11:23]

Done.

   }
-  // Set initial state.
-  DartUtils::SetIntegerField(library, "_port", server_port);
-  Dart_SetField(library,
-                DartUtils::NewString("_autoStart"),
-                Dart_NewBoolean(auto_start));
-  // We cannot register for signals on windows.
-#if defined(TARGET_OS_WINDOWS)
-  const bool is_windows = true;
-#else
-  const bool is_windows = false;
-#endif
-  Dart_SetField(library,
-                DartUtils::NewString("_isWindows"),
-                Dart_NewBoolean(is_windows));
 
-  // Invoke main.
-  result = Dart_Invoke(library, DartUtils::NewString("main"), 0, NULL);
-  SHUTDOWN_ON_ERROR(result);
-  // Load resources.
-  result = LoadResources(library);
-  SHUTDOWN_ON_ERROR(result);
+
+  {
+    // Get _getWatchSignalInternal from dart:io.
+    Dart_Handle dart_io_str = Dart_NewStringFromCString("dart:io");

[siva, 2014/09/09 00:40:58]

use DartUtils::kIOLibURL instead of "dart:io"

[Cutch, 2014/09/10 15:11:23]

Done.

+    Dart_Handle io_lib = Dart_LookupLibrary(dart_io_str);
+    Dart_Handle function_name =
+        Dart_NewStringFromCString("_getWatchSignalInternal");
+    Dart_Handle signal_watch = Dart_Invoke(io_lib, function_name, 0, NULL);
+    // Invoke main.
+    result =
+        Dart_Invoke(library, DartUtils::NewString("main"), 1, &signal_watch);
+    SHUTDOWN_ON_ERROR(result);
+  }

[siva, 2014/09/09 00:40:58]

Ditto question about why these two blocks are setup in special scopes?

[Cutch, 2014/09/10 15:11:23]

Done here and elsewhere.

 
   Dart_ExitScope();
   Dart_ExitIsolate();
 
   return true;
 }
 
 
 const char* VmService::GetErrorMessage() {
   return error_msg_ == NULL ? "No error." : error_msg_;
@@ skipping 128 matching lines @@
     printf("Service exited with an error:\n%s\n", Dart_GetError(result));
   }
   Dart_ExitScope();
   Dart_ExitIsolate();
 }
 
 
 
 }  // namespace bin
 }  // namespace dart