Yurii Shevtsov "V8 + libuv = Node.js. Under the hood"
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Node.js uses the V8 JavaScript engine and the libuv library. V8 compiles JavaScript to machine code for high performance, while libuv provides asynchronous I/O capabilities. Node.js initializes V8, wraps libuv, and provides a module system to load code, with modules defined as functions that export values. Native modules can extend Node.js using NAN or the newer N-API for direct access to V8 from C/C++ code.
![int func2(int arg1, char *arg2) {
char str[100];
/* some other expressions */
}
int func1() {
int foo = 0;
int bar = 3;
char* buzz = malloc(5);
func2(foo, buzz);
}
char* buzz (stack slot with
address)
int bar = 3
int foo = 3
Return address
Params of func1
Stack](https://image.slidesharecdn.com/shevtsovpresentationslides2017-170715185117/85/Yurii-Shevtsov-V8-libuv-Node-js-Under-the-hood-3-320.jpg)
![int func2(int arg1, char *arg2) {
char str[100];
/* some other expressions */
}
int func1() {
int foo = 0;
int bar = 3;
char* buzz = malloc(5);
func2(foo, buzz);
}
str[99]
str[1] … str[98]
str[0];
Return address (line 10)
arg2 = buzz
arg1 = foo = 3
Data of func1
Stack](https://image.slidesharecdn.com/shevtsovpresentationslides2017-170715185117/85/Yurii-Shevtsov-V8-libuv-Node-js-Under-the-hood-4-320.jpg)
![for (let i = 0; i < 42; i++) {}
foo[1]
foo[231]
Except SMI (Small integers)
2 42
570
200](https://image.slidesharecdn.com/shevtsovpresentationslides2017-170715185117/85/Yurii-Shevtsov-V8-libuv-Node-js-Under-the-hood-8-320.jpg)
![Your module is a function
NativeModule.wrap = function(script) {
return NativeModule.wrapper[0]+script+NativeModule.wrapper[1];
};
NativeModule.wrapper = [
'(function (exports, require, module, __filename, __dirname) { ',
'n});'
];](https://image.slidesharecdn.com/shevtsovpresentationslides2017-170715185117/85/Yurii-Shevtsov-V8-libuv-Node-js-Under-the-hood-41-320.jpg)
Yurii Shevtsov "V8 + libuv = Node.js. Under the hood"
- 1. V8 + libuv = Node.js Under the hood Юрий Шевцов
- 3. int func2(int arg1, char *arg2) { char str[100]; /* some other expressions */ } int func1() { int foo = 0; int bar = 3; char* buzz = malloc(5); func2(foo, buzz); } char* buzz (stack slot with address) int bar = 3 int foo = 3 Return address Params of func1 Stack
- 4. int func2(int arg1, char *arg2) { char str[100]; /* some other expressions */ } int func1() { int foo = 0; int bar = 3; char* buzz = malloc(5); func2(foo, buzz); } str[99] str[1] … str[98] str[0]; Return address (line 10) arg2 = buzz arg1 = foo = 3 Data of func1 Stack
- 5. Stackframe ● Arguments ● Local variables ● Return address
- 7. Everything is object on the Heap
- 8. for (let i = 0; i < 42; i++) {} foo[1] foo[231] Except SMI (Small integers) 2 42 570 200
- 9. Tagged pointer 32nd bit 1st bit Data bits T == 0 - SMI T == 1 - Pointer T X X X X X ... X X X X X X
- 11. Closer look JSObject Map Extra Properties Elements Property “a” Property “b” FixedArray Map Length Property “c” Property “d” FixedArray Map Length Property “1” Property “2” Property “3”
- 12. 32 Slots and extra properties 1. Object gets 32 slots 2. V8 trims unused slots later 3. Extra properties go separately
- 13. Elements ● Keys are array indices ● Elements may be represented as simple array ● Unbox values, if numbers only
- 14. Map a.k.a Hidden Class ● Stores object layout ({ property: offset }) ● Assignment order matters ● New map created for each object change ● Allows fast property lookup
- 15. Maps creation function Foo(bar, buzz) { this.bar = bar; this.buzz = buzz; } const foo1 = new Foo(1, 2); const foo2 = new Foo(3, 4); foo1.some = 5; { } - C0 { bar } - C1 { bar, buzz } - C2 { bar, buzz, some } - C3
- 16. Inline caching
- 17. Heap Structure New-space Old-space And more...
- 18. Garbage collection Scavenge | Mark & sweep
- 19. Mark
- 20. Compact
- 22. Asynchronicity <script type="text/javascript"> setTimeout(() => console.log(1)); Promise.resolve().then(() => console.log(2)); </script>
- 24. Task types Tasks: setTimeout, requestAnimationFrame, I/O, UI rendering Microtasks: Promises, process.nextTick, MutationObserver
- 25. Event loop algorithm 1. Run task till completion 2. Run microtasks 3. Run microtask scheduled by another microtask
- 26. Correct answer 2 1 Hint: running script is also a task
- 27. V8 compilers Before Full-codegen - generates unoptimized machine code Crankshaft - optimizes hot functions
- 28. V8 compilers Ignition - generates bytecode Turbofan - optimizes, using Sea-of-Nodes graph interpreter + compiler
- 29. V8 is a library
- 30. Bare V8 runs scripts Isolate* isolate = Isolate::New() Local<Context> context = Context::New(isolate) Local<String> source = String::New(isolate, "'Hello , World!'") Local<Script> script = Script::Compile(context, source) Local<Value> result = script->Run(context)
- 31. V8 API terminology Isolate - instance of V8 VM Context - holds pristine copy of global object Local<?> - handle for JS object in heap
- 33. Function Template void LogCallback(FunctionCallbackInfo<Value>& args) {} global->Set("log", FunctionTemplate::New(isolate, LogCallback));
- 35. Example global_templ->SetAccessor("foo", XGetter, XSetter); void XGetter(Local<String> property) { info.GetReturnValue().Set(x); } void XSetter(Local<String> property, Local<Value> value) { x = value->Int32Value(); } Local<ObjectTemplate> global = ObjectTemplate::New(isolate);
- 37. do { uv__update_time(loop); uv__run_timers(loop); uv__run_idle(loop); uv__run_prepare(loop); uv__io_poll(loop, timeout); uv__run_check(loop); uv__run_closing_handles(loop); } while (uv__loop_alive(loop))
- 40. Node.js is... ● V8 initializer ● libuv wrapper ● Module loader
- 41. Your module is a function NativeModule.wrap = function(script) { return NativeModule.wrapper[0]+script+NativeModule.wrapper[1]; }; NativeModule.wrapper = [ '(function (exports, require, module, __filename, __dirname) { ', 'n});' ];
- 42. Native modules NAN vs N-API