008 Web Assembly之性能分析
21 / 0 / 创建于 2年前
linghuyichong 的个人博客
0 介绍
视频地址：www.bilibili.com/video/BV1eg411g7c...
相关源码：github.com/anonymousGiga/Rust-and-...
本节我们将改进实现的生命游戏的性能，我们将利用时间分析来指导我们的工作。
1 使用window.performance.now函数创建FPS timer
FPS（Frames Per Second）Timer在我们分析康威游戏的渲染速度时非常有用。
我们首先添加fps对象到wasm-game-of-life/www/index.js中：
const fps = new class {
constructor() {
this.fps = document.getElementById("fps");
this.frames = [];
this.lastFrameTimeStamp = performance.now();
}
render() {
// Convert the delta time since the last frame render into a measure
// of frames per second.
const now = performance.now();
const delta = now - this.lastFrameTimeStamp;
this.lastFrameTimeStamp = now;
const fps = 1 / delta * 1000;
// Save only the latest 100 timings.
this.frames.push(fps);
if (this.frames.length > 100) {
this.frames.shift();
}
// Find the max, min, and mean of our 100 latest timings.
let min = Infinity;
let max = -Infinity;
let sum = 0;
for (let i = 0; i < this.frames.length; i++) {
sum += this.frames[i];
min = Math.min(this.frames[i], min);
max = Math.max(this.frames[i], max);
}
let mean = sum / this.frames.length;
// Render the statistics.
this.fps.textContent = `
Frames per Second:
latest = ${Math.round(fps)}
avg of last 100 = ${Math.round(mean)}
min of last 100 = ${Math.round(min)}
max of last 100 = ${Math.round(max)}
`.trim();
}
};再添加调用的代码：
const renderLoop = () => {
fps.render(); //new
universe.tick();
drawGrid();
drawCells();
animationId = requestAnimationFrame(renderLoop);
};在index.html中添加标签和响应的css代码，整个文件如下：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>game-of-life-canvas</title>
<style>
body {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
display: flex;
flex-direction: column;
align-items: center;
justify-content: center;
}
#fps {
white-space: pre;
font-family: monospace;
}
</style>
</head>
<body>
<button id="play-pause"></button>
<div id="fps"></div>
<!--canvas标签是表示图像或图表-->
<canvas id="game-of-life-canvas"></canvas>
<script src="./bootstrap.js"></script>
</body>
</html>输入127.0.0.1:8080可以看到已经可以在界面上显示帧率了。
2 分析每个tick的时间
我们使用web-sys中的console.time和console.timeEnd来分析Universe::tick。
我们在wasm-game-of-life/Cargo.toml中添加如下：
[dependencies.web-sys]
version = "0.3"
features = [
"console",
]为了方便调用，我们对console.timeEnd和console.time做如下封装：
use web_sys::console;
pub struct Timer<'a> {
name: &'a str,
}
impl<'a> Timer<'a> {
pub fn new(name: &'a str) -> Timer<'a> {
console::time_with_label(name);
Timer { name }
}
}
impl<'a> Drop for Timer<'a> {
fn drop(&mut self) {
console::time_end_with_label(self.name);
}
}然后我们在对应的方法中添加如下代码：
//在tick函数的第一行添加如下代码
let _timer = Timer::new("Universe::tick");编译后，我们可以使用F12查看相关的性能。
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