src: enable context snapshot after running per-context scripts

At build time, snapshot the context after running per-context scripts in the main instance, and in the final build, deserialize the context in the main instance. This provides a ~5% in the misc/startup benchmark when the instance is launched within a process that runs test/fixtures/semicolon.js. PR-URL: #27321 Refs: #17058 Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Refael Ackermann <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Ben Noordhuis <[email protected]>
nodejs · Apr 27, 2019 · 228127f · 228127f
1 parent 45d6106
commit 228127f
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Showing 3 changed files with 10 additions and 1 deletion.
diff --git a/src/node_main_instance.cc b/src/node_main_instance.cc
@@ -171,9 +171,13 @@ std::unique_ptr<Environment> NodeMainInstance::CreateMainEnvironment(
     isolate_->GetHeapProfiler()->StartTrackingHeapObjects(true);
   }
 
-  Local<Context> context = NewContext(isolate_);
+  Local<Context> context;
   if (deserialize_mode_) {
+    context =
+        Context::FromSnapshot(isolate_, kNodeContextIndex).ToLocalChecked();
     SetIsolateUpForNode(isolate_, IsolateSettingCategories::kErrorHandlers);
+  } else {
+    context = NewContext(isolate_);
   }
 
   CHECK(!context.IsEmpty());

diff --git a/src/node_main_instance.h b/src/node_main_instance.h
@@ -75,6 +75,8 @@ class NodeMainInstance {
   static const IndexArray* GetIsolateDataIndexes();
   static v8::StartupData* GetEmbeddedSnapshotBlob();
 
+  static const size_t kNodeContextIndex = 0;
+
  private:
   NodeMainInstance(const NodeMainInstance&) = delete;
   NodeMainInstance& operator=(const NodeMainInstance&) = delete;

diff --git a/tools/snapshot/snapshot_builder.cc b/tools/snapshot/snapshot_builder.cc
@@ -104,6 +104,9 @@ std::string SnapshotBuilder::Generate(
       HandleScope scope(isolate);
       creator.SetDefaultContext(Context::New(isolate));
       isolate_data_indexes = main_instance->isolate_data()->Serialize(&creator);
+
+      size_t index = creator.AddContext(NewContext(isolate));
+      CHECK_EQ(index, NodeMainInstance::kNodeContextIndex);
     }
 
     // Must be out of HandleScope