JavaScript 引擎性能比较之二Google V8

Google V8 如日中天, 凭借 Chrome 和 NodeJS 两款应用, 在开发者中有极好的口碑

先下载 v8 编译生成若干所需的库文件

# 项目主页
https://code.google.com/p/v8/

# 编译安装, 得先安装 gjt, depot_tools , 参见以下链接, 在此略过
* https://code.google.com/p/v8-wiki/wiki/BuildingWithGYP

# 参考资料, 可能需
* https://developers.google.com/v8/embed
* https://developers.google.com/v8/get_started
* https://code.google.com/p/v8-wiki/wiki/BuildingWithGYP

# 测试程序 makefile.am如下, 测试环境为 macbook air,  osx 10.10.3, Darwin Kernel Version 14.3.0 , 

V8Test_SOURCES = v8test.cpp 
V8Test_CPPFLAGS = -I$(top_srcdir)/third_party/v8 -I$(top_srcdir)/util -pthread -lrt -stdlib=libstdc++ -std=c++11
V8Test_LDFLAGS =  -L/workspace/cpp/v8/xcodebuild/Release -L$(top_srcdir)/util -stdlib=libstdc++ -std=c++11
V8Test_LDADD = -lv8_base -lv8_libbase -lv8_snapshot -lv8_libplatform -licuuc -licui18n -licudata

还是和上一篇一样的 javascript arraysort.js:

function random_str()
{
    var text = "";
    var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

    for( var i=0; i < 8; i++ )
        text += possible.charAt(Math.floor(Math.random() * possible.length));

    return text;
}

var array = new Array();
for ( var i = 0; i < 10000; i++) 
{
	array[array.length] = random_str();
}
debug_trace("begin sort and reverse array which length=" + array.length );

array.sort();
array.reverse();

debug_trace("done, first element=" + array[0]+ ", " + "last element=" + array[array.length-1] );

现在由 V8 来执行, 看看测试结果如何

废话不多说, 先上源码 v8test.cpp, 根据 V8 自带的 shell.cc 改写而来

#include "include/v8.h"
#include "include/libplatform/libplatform.h"


using namespace v8;

long long current_timestamp(char arrTimeStr[TIME_FMT_LEN]) {

    struct timeval tv;
    struct tm* ptm;
    char time_string[40];


    gettimeofday(&tv, NULL); // get current time
    if (arrTimeStr) {
        ptm = localtime(&tv.tv_sec);
        /* Format the date and time, down to a single second.  */
        strftime(time_string, sizeof(time_string), "%Y-%m-%d %H:%M:%S", ptm);
        /* Compute milliseconds from microseconds.  */
        //snprintf(char * restrict str, size_t size, const char * restrict format,
        snprintf(arrTimeStr, TIME_FMT_LEN, "%s.%06d", time_string, tv.tv_usec);
    }
    long long total_us = tv.tv_sec * 1000000LL + tv.tv_usec ; // caculate milliseconds
    // printf("milliseconds: %lld\n", milliseconds);
    return total_us;
}

// Extracts a C string from a V8 Utf8Value.
const char* ToCString(const v8::String::Utf8Value& value) {
  return *value ? *value : "";
}

void debug_trace(const v8::FunctionCallbackInfo& args) 
{
  
  if (args.Length() > 0) {
      char szTimeStr[TIME_FMT_LEN] = { '\0' };
      current_timestamp(szTimeStr);
	  
      v8::String::Utf8Value str(args[0]);
      const char* cstr = ToCString(str);
	  
      printf("[%s] %s\n", szTimeStr, cstr);
  }

}

v8::Handle ReadFile(v8::Isolate* isolate, const char* name) {
  FILE* file = fopen(name, "rb");
  if (file == NULL) return v8::Handle();

  fseek(file, 0, SEEK_END);
  int size = ftell(file);
  rewind(file);

  char* chars = new char[size + 1];
  chars[size] = '\0';
  for (int i = 0; i < size;) {
    int read = static_cast(fread(&chars[i], 1, size - i, file));
    i += read;
  }
  fclose(file);
  v8::Handle result =
      v8::String::NewFromUtf8(isolate, chars, v8::String::kNormalString, size);
  delete[] chars;
  return result;
}

v8::Handle CreateShellContext(v8::Isolate* isolate) {
  // Create a template for the global object.
  v8::Handle global = v8::ObjectTemplate::New(isolate);
  // Bind the global 'print' function to the C++ Print callback.
  global->Set(v8::String::NewFromUtf8(isolate, "debug_trace"),
              v8::FunctionTemplate::New(isolate, debug_trace));

  return v8::Context::New(isolate, NULL, global);
}

void ReportException(v8::Isolate* isolate, v8::TryCatch* try_catch) {
  v8::HandleScope handle_scope(isolate);
  v8::String::Utf8Value exception(try_catch->Exception());
  const char* exception_string = ToCString(exception);
  v8::Handle message = try_catch->Message();
  if (message.IsEmpty()) {
    // V8 didn't provide any extra information about this error; just
    // print the exception.
    fprintf(stderr, "%s\n", exception_string);
  } else {
    // Print (filename):(line number): (message).
    v8::String::Utf8Value filename(message->GetScriptOrigin().ResourceName());
    const char* filename_string = ToCString(filename);
    int linenum = message->GetLineNumber();
    fprintf(stderr, "%s:%i: %s\n", filename_string, linenum, exception_string);
    // Print line of source code.
    v8::String::Utf8Value sourceline(message->GetSourceLine());
    const char* sourceline_string = ToCString(sourceline);
    fprintf(stderr, "%s\n", sourceline_string);
    // Print wavy underline (GetUnderline is deprecated).
    int start = message->GetStartColumn();
    for (int i = 0; i < start; i++) {
      fprintf(stderr, " ");
    }
    int end = message->GetEndColumn();
    for (int i = start; i < end; i++) {
      fprintf(stderr, "^");
    }
    fprintf(stderr, "\n");
    v8::String::Utf8Value stack_trace(try_catch->StackTrace());
    if (stack_trace.length() > 0) {
      const char* stack_trace_string = ToCString(stack_trace);
      fprintf(stderr, "%s\n", stack_trace_string);
    }
  }
}


// Executes a string within the current v8 context.
bool ExecuteString(v8::Isolate* isolate,
                   v8::Handle source,
                   v8::Handle name,
                   bool print_result,
                   bool report_exceptions) {
  v8::HandleScope handle_scope(isolate);
  v8::TryCatch try_catch;
  v8::ScriptOrigin origin(name);
  v8::Handle script = v8::Script::Compile(source, &origin);
  if (script.IsEmpty()) {
    // Print errors that happened during compilation.
    if (report_exceptions)
      ReportException(isolate, &try_catch);
    return false;
  } else {
    v8::Handle result = script->Run();
    if (result.IsEmpty()) {
      assert(try_catch.HasCaught());
      // Print errors that happened during execution.
      if (report_exceptions)
        ReportException(isolate, &try_catch);
      return false;
    } else {
      assert(!try_catch.HasCaught());
      if (print_result && !result->IsUndefined()) {
        // If all went well and the result wasn't undefined then print
        // the returned value.
        v8::String::Utf8Value str(result);
        const char* cstr = ToCString(str);
        printf("%s\n", cstr);
      }
      return true;
    }
  }
}

int main(int argc, char* argv[]) {
  // Initialize V8.
  V8::InitializeICU();
  Platform* platform = platform::CreateDefaultPlatform();
  V8::InitializePlatform(platform);
  V8::Initialize();

  // Create a new Isolate and make it the current one.
  Isolate* isolate = Isolate::New();
  {
    Isolate::Scope isolate_scope(isolate);

    // Create a stack-allocated handle scope.
    HandleScope handle_scope(isolate);

    // Create a new context.
     v8::Handle context = CreateShellContext(isolate);
     if (context.IsEmpty()) {
       fprintf(stderr, "Error creating context\n");
       return 1;
     }
	 
    // Enter the context for compiling and running the hello world script.
    Context::Scope context_scope(context);
	
    // Create a string containing the JavaScript source code.
    Local source;
	Local filename;

    if (argc > 1) {
		filename = String::NewFromUtf8(isolate, argv[1]);
		source = ReadFile(isolate, argv[1]);
    } else {
    	source = String::NewFromUtf8(isolate, "'Hello' + ', World!'");
		filename = String::NewFromUtf8(isolate, "nofile");
    }

    long long begin_time = current_timestamp(NULL);
  	ExecuteString(isolate, source,filename, false, true);
    long long end_time = current_timestamp(NULL);
    printf("calling costs %lld microseconds\n", end_time - begin_time);
  }
  
  // Dispose the isolate and tear down V8.
  isolate->Dispose();
  V8::Dispose();
  V8::ShutdownPlatform();
  delete platform;
  return 0;
}

对照测试结果如下

SpiderMonkey 执行此 JS 文件共花费了 46.781 ms, 其中一万个元素的字符串数组排序反转花费了 3 ms 不到的时间

$ ./test/SpiderMonkeyTest ./test/arraysort.js
[2015-05-10 08:22:20.246747] begin sort and reverse array which length=10000
[2015-05-10 08:22:20.249263] done, first element=zzvJWaQw, last element=00BpApzs
calling costs 46781 microseconds

V8 执行此 JS 文件共花费了 22.326 ms, 其中一万个元素的字符串数组排序反转花费了约 9 ms 

$ ./test/V8Test ./test/arraysort.js
[2015-05-10 08:22:34.324314] begin sort and reverse array which length=10000
[2015-05-10 08:22:34.337588] done, first element=zzmBlrhz, last element=00G00Ssm
calling costs 22326 microseconds

总时间 V8 果然名不虚传, 总的执行比 spidermonkey 快了一倍多, 但有趣的是在内部的字符串数组排序反转所花费的时间方面 SpiderMonkey 反而遥遥领先, 有待研究