Unity Issue Tracker - Canvas.BuildBatch 50% - 70% CPU spikes when dragging mouse from Unity window to any other OS window

Fixed in 2020.1.X

Fixed in 2018.4.X

Votes

2

Found in

2018.3.5f1

2018.4.0f1

2019.1.0a1

2019.1.13f1

2019.3.0a7

2020.1.0a1

Issue ID

1175268

Regression

Yes

Canvas.BuildBatch 50% - 70% CPU spikes when dragging mouse from Unity window to any other OS window

Graphics - General

-

Aug 08, 2019

To reproduce:
1. Open "ExtractedScene 2019.1.zip" project
2. Open "reproTryVeryMin.unity" scene
3. Enter Play mode
4. Scroll on the white block on the left
5. Observe Profiler
6. Drag mouse between macOS dock and Unity Editor

Expected: Canvas.BuildBatch CPU usage should be 0.1% - 4%
Actual result: getting 50% - 70% CPU spikes on Canvas.BuildBatch

Reproduced on:
2018.3.5f1 2018.4.0f1 2019.1.14f1 2019.3.0a7 2019.3.0b1 2020.1.0a1

Not reproduced on:
2017.4.32f1 2019.2.3f1 2019.3.0a6 (getting about 0.1% - 0.5% usage)

Notes:
- Reproduction video in edit
- On 2019.3.0a6 getting the same spikes but up to 20%
- 2018.3.2f1 - 2018.3.4f1 getting the same spikes but Canvas.BuildBatch is using 0.1% - 4%
- In 2018.3.0a1 - 2018.3.0f1 constant spikes are appearing but the Profiler window shows only 0.1% - 4% CPU usage in Canvas.BuildBatch (1830a1.png)