Memory map heap snapshot blob file

src/jni/File.cpp

@@ -8,6 +8,11 @@
 #include "File.h"
 #include <sstream>
 #include <fstream>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <assert.h>
 
 using namespace std;
 
@@ -98,6 +103,41 @@ namespace tns
 		return Buffer;
 	}
 
+	MemoryMappedFile MemoryMappedFile::Open(const char* filePath)
+	{
+		void* memory = nullptr;
+		int length = 0;
+		if (FILE* file = fopen(filePath, "r+"))
+		{
+			if (fseek(file, 0, SEEK_END) == 0)
+			{
+				length = ftell(file);
+				if (length >= 0)
+				{
+					memory = mmap(NULL, length, PROT_READ, MAP_SHARED, fileno(file), 0);
+					if (memory == MAP_FAILED)
+					{
+						memory = nullptr;
+					}
+				}
+			}
+			fclose(file);
+		}
+		return MemoryMappedFile(memory, length);
+	}
+
+	MemoryMappedFile::MemoryMappedFile(void* memory, size_t size)
+	:
+			memory(memory), size(size)
+	{
+	}
+
+	MemoryMappedFile::~MemoryMappedFile()
+	{
+		int result = munmap(this->memory, this->size);
+		assert(result == 0);
+	}
+
 	char* File::Buffer = new char[BUFFER_SIZE];
 
 	const char* File::WRITE_BINARY = "wb";

src/jni/File.h

@@ -12,6 +12,16 @@
 
 namespace tns
 {
+	struct MemoryMappedFile final
+	{
+			static MemoryMappedFile Open(const char* filePath);
+			MemoryMappedFile(void* memory, size_t size);
+			~MemoryMappedFile();
+
+			void* memory = nullptr;
+			size_t size = 0;
+	};
+
 	class File
 	{
 		public:

src/jni/Runtime.cpp

@@ -17,7 +17,6 @@
 #include "JsDebugger.h"
 #include "SimpleProfiler.h"
 #include "SimpleAllocator.h"
-#include "File.h"
 #include "JType.h"
 #include "Module.h"
 #include "NativeScriptException.h"
@@ -58,7 +57,6 @@ Runtime::Runtime(JNIEnv *env, jobject runtime, int id)
 {
 	m_runtime = m_env.NewGlobalRef(runtime);
 	m_objectManager = new ObjectManager(m_runtime);
-	m_startupData = nullptr;
 	s_id2RuntimeCache.insert(make_pair(id, this));
 }
 
@@ -339,10 +337,8 @@ void Runtime::PassUncaughtExceptionToJsNative(JNIEnv *env, jobject obj, jthrowab
 }
 
 void Runtime::ClearStartupData(JNIEnv *env, jobject obj) {
-	if (m_startupData) {
-		delete m_startupData->data;
-		delete m_startupData;
-	}
+	delete m_heapSnapshotBlob;
+	delete m_startupData;
 }
 
 Isolate* Runtime::PrepareV8Runtime(const string& filesPath, jstring packageName, jobject jsDebugger, jstring profilerOutputDir)
@@ -377,11 +373,11 @@ Isolate* Runtime::PrepareV8Runtime(const string& filesPath, jstring packageName,
 
 		if (File::Exists(snapshotPath))
 		{
-			int length;
-			m_startupData->data = reinterpret_cast<char*>(File::ReadBinary(snapshotPath, length));
-			m_startupData->raw_size = length;
+			m_heapSnapshotBlob = new MemoryMappedFile(MemoryMappedFile::Open(snapshotPath.c_str()));
+			m_startupData->data = static_cast<const char*>(m_heapSnapshotBlob->memory);
+			m_startupData->raw_size = m_heapSnapshotBlob->size;
 
-			DEBUG_WRITE_FORCE("Snapshot read %s (%dB).", snapshotPath.c_str(), length);
+			DEBUG_WRITE_FORCE("Snapshot read %s (%dB).", snapshotPath.c_str(), m_heapSnapshotBlob->size);
 		}
 		else if(saveSnapshot)
 		{

src/jni/Runtime.h

@@ -8,6 +8,7 @@
 #include "WeakRef.h"
 #include "ArrayBufferHelper.h"
 #include "Profiler.h"
+#include "File.h"
 
 jobject ConvertJsValueToJavaObject(tns::JEnv& env, const v8::Local<v8::Value>& value, int classReturnType);
 
@@ -58,7 +59,8 @@ namespace tns
 
 			Profiler m_profiler;
 
-			v8::StartupData *m_startupData;
+			v8::StartupData *m_startupData = nullptr;
+			MemoryMappedFile *m_heapSnapshotBlob = nullptr;
 
 			static void PrepareExtendFunction(v8::Isolate *isolate, jstring filesPath);
 			v8::Isolate* PrepareV8Runtime(const std::string& filesPath, jstring packageName, jobject jsDebugger, jstring profilerOutputDir);