<p dir="auto"><a href="https://mp.weixin.qq.com/s/j9ibj4ZYAqNZwwvSpIAtLA" rel="nofollow">https://mp.weixin.qq.com/s/j9ibj4ZYAqNZwwvSpIAtLA</a> states a 64% simulator CPU usage which is plausible but also seems like a bug.</p>
<p dir="auto">Could be related to <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="276881482" data-permission-text="Title is private" data-url="https://github.com/flutter/flutter/issues/13203" data-hovercard-type="issue" data-hovercard-url="/flutter/flutter/issues/13203/hovercard" href="https://github.com/flutter/flutter/issues/13203">#13203</a> and/or iOS simulator only too</p>
<h2 dir="auto">Steps to Reproduce</h2>
<p dir="auto">Create a widget below:</p>
<div class="highlight highlight-source-dart notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="class Loading extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Column(mainAxisAlignment: MainAxisAlignment.center, children: [
      new Center(child: const CupertinoActivityIndicator()),
      const Padding(padding: const EdgeInsets.only(top: 8.0)),
      new Center(child: new Text(&quot;Loading...&quot;))
    ]);
  }
}"><pre class="notranslate"><span class="pl-k">class</span> <span class="pl-c1">Loading</span> <span class="pl-k">extends</span> <span class="pl-c1">StatelessWidget</span> {
  <span class="pl-k">@override</span>
  <span class="pl-c1">Widget</span> <span class="pl-en">build</span>(<span class="pl-c1">BuildContext</span> context) {
    <span class="pl-k">return</span> <span class="pl-k">new</span> <span class="pl-c1">Column</span>(mainAxisAlignment<span class="pl-k">:</span> <span class="pl-c1">MainAxisAlignment</span>.center, children<span class="pl-k">:</span> [
      <span class="pl-k">new</span> <span class="pl-c1">Center</span>(child<span class="pl-k">:</span> <span class="pl-k">const</span> <span class="pl-c1">CupertinoActivityIndicator</span>()),
      <span class="pl-k">const</span> <span class="pl-c1">Padding</span>(padding<span class="pl-k">:</span> <span class="pl-k">const</span> <span class="pl-c1">EdgeInsets</span>.<span class="pl-en">only</span>(top<span class="pl-k">:</span> <span class="pl-c1">8.0</span>)),
      <span class="pl-k">new</span> <span class="pl-c1">Center</span>(child<span class="pl-k">:</span> <span class="pl-k">new</span> <span class="pl-c1">Text</span>(<span class="pl-s">"Loading..."</span>))
    ]);
  }
}</pre></div>
<p dir="auto">Then run on a simulator, "top -o cpu"</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="PID    COMMAND      %CPU
13241  backboardd   128.3
13661  Runner       99.7"><pre class="notranslate"><code class="notranslate">PID    COMMAND      %CPU
13241  backboardd   128.3
13661  Runner       99.7
</code></pre></div>
<p dir="auto">Then press 'q', the CPU drop to zero.</p>
<h2 dir="auto">Flutter Doctor</h2>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="[✓] Flutter (on Mac OS X 10.13.1 17B48, locale en-HK, channel master)
    • Flutter at /Users/odd/wa/flutter/flutter
    • Framework revision bdbe53be01 (2 days ago), 2017-11-24 19:13:18 -0800
    • Engine revision 93b2179597
    • Tools Dart version 1.25.0-dev.11.0

[✓] Android toolchain - develop for Android devices (Android SDK 26.0.2)
    • Android SDK at /Users/odd/Library/Android/sdk
    • Unable to locate Android NDK.

    • Unable to locate compiler in Android NDK.

    • Platform android-26, build-tools 26.0.2
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] iOS toolchain - develop for iOS devices (Xcode 9.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 9.1, Build version 9B55
    • ios-deploy 1.9.2
    • CocoaPods version 1.3.1

[✓] Android Studio (version 2.3)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] Connected devices
    • iPhone X • 2B869FE0-C8D2-4755-9C69-D0F91CED8588 • ios • iOS 11.1 (simulator)"><pre class="notranslate"><code class="notranslate">[✓] Flutter (on Mac OS X 10.13.1 17B48, locale en-HK, channel master)
    • Flutter at /Users/odd/wa/flutter/flutter
    • Framework revision bdbe53be01 (2 days ago), 2017-11-24 19:13:18 -0800
    • Engine revision 93b2179597
    • Tools Dart version 1.25.0-dev.11.0

[✓] Android toolchain - develop for Android devices (Android SDK 26.0.2)
    • Android SDK at /Users/odd/Library/Android/sdk
    • Unable to locate Android NDK.

    • Unable to locate compiler in Android NDK.

    • Platform android-26, build-tools 26.0.2
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] iOS toolchain - develop for iOS devices (Xcode 9.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 9.1, Build version 9B55
    • ios-deploy 1.9.2
    • CocoaPods version 1.3.1

[✓] Android Studio (version 2.3)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] Connected devices
    • iPhone X • 2B869FE0-C8D2-4755-9C69-D0F91CED8588 • ios • iOS 11.1 (simulator)
</code></pre></div>