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Fixed in 2020.1.X

Fixed in 2018.4.X, 2019.3.X



Found in






Issue ID




Semaphore.WaitForSignal under Canvas.BuildBatch causes a slow editor in Play mode

Visual Effects - Legacy


Steps to reproduce:
1. Open the attached project "Temp Project" from the ownCloud link
2. Open "Main Scene"
3. Turn on the Profiler window
4. Enter Play mode
5. Notice the Spikes from Semaphore.WaitForSignal

Expected results: Semaphore.WaitForSignal does not cause spikes in the Profiler window and making Editor slow
Actual results: Semaphore.WaitForSignal causes spikes in the Profiler window and makes Editor slow

Reproducible with: 2019.2.3f1, 2019.3.0b1, 2020.1.0a1

Note: 2019.1 breaks the project and its packages

  1. richardkettlewell

    Oct 16, 2019

    We are working on a fix for this.

Comments (39)

  1. Dimonasdf

    Dec 25, 2019 15:43

    2019.2.17 stiil has this issue

  2. TheAnubis

    Dec 22, 2019 11:01

    It happens to me in Unity 2019.3.03f as well

  3. hawkigamer

    Dec 20, 2019 22:02

    Found in unity 2019.3.0f3

  4. KingVario

    Dec 13, 2019 14:09

    Same issue here 2019.3.0f3 Windows 10 and Android 9 reproduces this error when building game standalone for windows or android with autoconnect profiler.
    Inside editor the Semaphore high MS does not appear when profiling only when i build external development build.
    This Semaphore severely skews other profiler data.

  5. PhilipKeenanPhilips

    Dec 12, 2019 20:40

    Still have this issue in Unity 2013.3.0f3

  6. SebMarello

    Dec 12, 2019 13:40

    Same issue 2019.2.15f1

  7. antrikshvatss

    Nov 25, 2019 13:45

    I am getting this issue in unity 2019.3 beta version as well as 2020.1 alpha version

  8. NewMagic-Studio

    Nov 24, 2019 21:20

    Same problem using 2019.2.11 have Semaphore.WaitForSignal inside MeshSkinning.Update using 33% of CPU

  9. antrikshvatss

    Nov 23, 2019 15:41

    Is this issue fixed in unity 2019.3.0b11

  10. pixelR

    Nov 12, 2019 10:47

    Is this the same reason why I have WaitForSignal in my Android game on the mobile? Unity 2019.3.0b10 + URP 7.1.2

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