Garbage collectors and Memory Leaks in Nodejs - V8
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This document provides an overview of garbage collectors and memory management in Node.js v8, including the functioning of major and minor garbage collection. It highlights best practices for memory debugging and offers insights on profiling applications using frameworks like MemLab and Chrome DevTools. Additional resources for deeper understanding of V8's architecture and memory management strategies are also included.
![▶About V8 Garbage Collection
About V8 Garbage Collection
- Stack vs Heap mem
const a1 = 12;
let b1 = a1;
b1 += 1;
const s1 = 'string herer';
const array1 =
[{value:a1},{value:b1}];](https://image.slidesharecdn.com/garbagecollectorsandmemoryleaksinnodejs-v8-221208042700-87de8be1/85/Garbage-collectors-and-Memory-Leaks-in-Nodejs-V8-9-320.jpg)
![▶Best practises and notes
- Limit global variable
- Using short-live object
- Always give name to closures and function -> easy to debug
- Avoid Closures variables:
- Avoid Timer
- Using the dispose pattern, like vscode
- Avoid polymorphism for IC in hot func
// Avoid Closures variables
function clickHandleFactory(){
const eventStore = []; // this never be
collected by gc
return function (event) {
eventStore.push(event);
}
}
const clickHandle = function clickHandleFactory();
button.addEventListener('click',clickHandle);](https://image.slidesharecdn.com/garbagecollectorsandmemoryleaksinnodejs-v8-221208042700-87de8be1/85/Garbage-collectors-and-Memory-Leaks-in-Nodejs-V8-21-320.jpg)
Garbage collectors and Memory Leaks in Nodejs - V8
- 2. ▶Garbage Collectors and Memory Leaks in Node.js V8 Thien Ly - Engineer at Tiki Tiki Tini App Workshop Nov 10, 2022
- 3. ▶ Main Checkpoints A. 🔥Technical Facts 1. A quick glance at V8 ● About V8 ● V8’s compiler pipeline 1. About V8 Garbage Collection ● Garbage Collector: ▶ Major GC (Mark- Compact) ● Garbage Collector: ▶ Minor GC (Scavenger) ● Hidden class ● Inline Cache ● Hot function 1. Best practices with GC B. 🛡️Practising Memory debugging 1) Profiling frontend app memory with Memlab framework from Facebook 2) Profiling backend app memory: inspect node app with Chrome Devtools
- 4. A.Technical Facts 1. A quick glance at V8 ▶ Garbage Collectors and Memory Leaks in Node.js V8
- 5. ▶A Quick glance at V8 About V8 - “V8 is Google's open source high-performance JavaScript and WebAssembly engine, written in C++. It is used in Chrome and in Node.js, among others.” (v8.dev) - Initial release date: Sep 2, 2008 - V8 alternatives: - SpiderMonkey - JavaScriptCore(JSC) - Chakra - JerryScript
- 6. ▶A Quick glance at V8 V8’s compiler pipeline V8’s compiler pipeline Source: Franziska Hinkelmann, Ph.D. - Understanding V8’s Bytecode
- 7. ▶A Quick glance at V8 V8’s compiler pipeline – Other Resources: Dig into old versions of V8 compiler pipeline and the Ignition: V8: Hooking up the Ignition to the Turbofan by Leszek Swirski & Ross McIlroy
- 8. A.Technical Facts 2. About V8 Garbage Collection ▶ Garbage Collectors and Memory Leaks in Node.js V8
- 9. ▶About V8 Garbage Collection About V8 Garbage Collection - Stack vs Heap mem const a1 = 12; let b1 = a1; b1 += 1; const s1 = 'string herer'; const array1 = [{value:a1},{value:b1}];
- 10. ▶About V8 Garbage Collection Stack vs heap mem - Stack: fixed size; stores static data, includes primitive values like strings, numbers, boolean, null, and undefined. References that point to objects and functions. - Heap: stores objects and functions in JavaScript. “Objects” in this context mean objects in JavaScript, functions, and scopes > In V8, they divides the heap memory space into 2 regions: young generation and old generation.
- 11. ▶About V8 Garbage Collection Overview of memory management in v8 https://deepu.tech/memory-management-in-v8/
- 12. ▶About V8 Garbage Collection Major GC (Full Mark-Compact) — “The major GC collects garbage from the entire heap. Marking →Sweeping → Compaction(defragmentation); - Super slow; - “Stop the world”; v8.dev
- 13. ▶About V8 Garbage Collection Garbage Collector: ▶ Major GC (Mark-Compact) Mark ⇒ Sweep ⇒ Compact(defragmentation)
- 14. ▶About V8 Garbage Collection Major GC (Full Mark-Compact) — “The major GC collects garbage from the entire heap. Marking →Sweeping → Compaction(defragmentation); - Super slow; - “Stop the world”; v8.dev
- 15. ▶About V8 Garbage Collection Minor GC (Scavenger) v8.dev
- 16. ▶About V8 Garbage Collection Minor GC (Scavenger) v8.dev
- 17. ▶About V8 Garbage Collection Minor GC (Full Mark-Compact) - Move mem that is using in heap from A to B - Compact: re-arrange(just like defrag a hdd) - Swap A and B, delete the old A ( I mean B now ) - If obj is moved twice, move it to Old generation space for Major GC handle later v8.dev
- 18. ▶About V8 Garbage Collection Hidden Class - Once object created, V8 also creates a Hidden class to track its props - Every object shape changes(add/delete object’s properties) create one hidden class - Support V8 Tracking and Inline Caching - Objects with the same shape share the same HC const a1 = {a:2}; const a2 = {a:99}; // a2 and a1 are using the same hidden class because of their shape.
- 19. ▶About V8 Garbage Collection Hidden Class var obj = {}; obj.x = 1; obj.y = 2
- 20. ▶About V8 Garbage Collection Inline Caching (IC) - Optimization technique - Rely on the observation that repeated calls to same function tends to occur on same type of objects. - Types: - Monomorphic (optimized) - Polymorphic (slightly optimized) - Megamorphic (unoptimized) // (lv 5 for default, – max_inlining_levels flag)
- 21. ▶Best practises and notes - Limit global variable - Using short-live object - Always give name to closures and function -> easy to debug - Avoid Closures variables: - Avoid Timer - Using the dispose pattern, like vscode - Avoid polymorphism for IC in hot func // Avoid Closures variables function clickHandleFactory(){ const eventStore = []; // this never be collected by gc return function (event) { eventStore.push(event); } } const clickHandle = function clickHandleFactory(); button.addEventListener('click',clickHandle);
- 22. ▶Best practises - Detached dom checking
- 23. B. Practising Memory debugging 1. Profiling frontend app memory with Memlab framework from Facebook ▶ Garbage Collectors and Memory Leaks in Node.js V8
- 24. ▶Profiling FE app memory with Memlab About Memlab - Open source by facebook - Memory testing framework for js - Under the hood: puppeteer > chrome devtool protocol Prepare: - Install memlab with node 16: npm install -g memlab - Start your own web app
- 25. ▶Profiling FE app memory with Memlab Demo
- 26. ▶Profiling FE app memory with Memlab Supports Jest testing in Node Example import type {IHeapSnapshot} from '@memlab/core'; import {config, takeNodeMinimalHeap, tagObject} from '@memlab/core'; function unitToTest(obj){ // example app unit logic obj.o2 = null; } test('should release targeted object', async () => { config.muteConsole = true; const owner = {o1:{},o2:{}}; tagObject(owner.o1, 'flag-1'); tagObject(owner.o2, 'flag-2'); unitToTest(owner); const heap: IHeapSnapshot = await takeNodeMinimalHeap(); expect(heap.hasObjectWithTag('flag-1')).toBe(true); expect(heap.hasObjectWithTag('flag-2')).toBe(false); }, 30000);
- 27. B. Practising Memory debugging 2. Profiling BE app memory: inspect nodejs with chrome devtool ▶ Garbage Collectors and Memory Leaks in Node.js V8
- 28. ▶Profiling BE app memory: inspect nodejs with chrome devtool Demo
- 29. ▶References and further reads - Understanding V8's Bytecode - Franziska Hinkelmann, Ph.D., 2017 - https://www.fhinkel.rocks/posts/Understanding-V8-s-Bytecode; - Launching Ignition and TurboFan, 2017 - https://v8.dev/blog/launching-ignition- and-turbofan; - Trash talk: the Orinoco garbage collector, 2019 - https://v8.dev/blog/trash-talk; - Leszek Swirski & Ross McIlroy, 2017 - Hooking up the Ignition to the Turbofan by Leszek Swirski & Ross McIlroy; - Deepu K Sasidharan - Visualizing memory management in V8 Engine (JavaScript, NodeJS, Deno, WebAssembly), 2018 - https://deepu.tech/memory- management-in-v8/;
- 30. ❯ (Q && A) || SIGTERM Send your questions via Tiki Developer Community: - https://community.tiki.vn/t/building-a- super-app-workshop-sharing- garbage-collectors-and-memory- leaks-in-nodejs-v8/8548 ❯ echo 'Gracias ♡ ~' | lolcat