涟漪图-effectScatter-加上后cpu占用率从5%跳到38%左右，请问如何解决？

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- [x ] Required: demo；（必填）能反映问题的例子（如果你想提问或报 bug）
- [ x] Required: ECharts version；ECharts 版本

## Issue Type

- [ ] I have a question to ask about *how to use ECharts to ...*；我想提问如何使用 ECharts 实现某功能
- [x ] I have a bug to report；我想要报 bug
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## Issue Details

我在geo地图中使用了effectScatter后，cpu占用率激增

### Expected Behavior

能够降低cpu占用

### Current Behavior

cpu占用30%以上

### Online Example

地图渲染后如下：

占用率如下（火狐浏览器）：

{
name: '涟漪图',
type: 'effectScatter',
showEffectOn: 'render',
coordinateSystem: 'geo',
rippleEffect: {
period: 6,
scale: 6,
brushType: 'fill' // 动画中波纹的最大缩放比例。stroke fill
},
animation: false,
// data: seriesData.fluxSeriesData,
data: [
{
"symbolSize": 12,
"itemStyle": {
"color": "rgba(250,58,71,0.6)"
},
"value": [
"116.403039",
"39.914909"
]
}
],
z: 1
}

## Topics

- [ ] Legend
- [ ] Tooltip
- [ ] Event
- [ ] Performance
- [ ] SVG
- [ ] Map
- [ ] ECharts GL
- [ ] Third-party libraries, e.g.: Vue.js, React

## Anything Else We Need to Know

{DESCRIBE_HERE}

## Environment

- ECharts version；ECharts 版本: 4.0.4

- [ ] It happens only on certain browsers or operating systems. 对于特定浏览器或操作系统才会出现的问题，请提供相应环境信息：{BROWSER_VERSION_OR_OS_INFORMATION_HERE}