Semaphore Wait for signal accounts for 80% of total cpu usage.

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As seen in the screenshot semaphore.WaitForSignal is costing up to 5.37 ms per frame. That is roughly 80% of my entire game's cpu usage.

Sometimes I will get random spikes of up to 400ms due to the same reason causing my game to stutter horribly.

It is a 3d game with no lighting. I'm using unlit shaders only. My biggest texture is 1536 x 1536 which I'm only mapping on a single object.

How can I reduce or eliminate this?

Answer 1

Answer by ArminRigo · Jan 24, 2020 at 09:23 AM

It just means the main thread is sleeping, waiting for a signal from another thread. It's not actually consuming CPU time. The render thread is working instead, and I guess that at some point this render thread signals the main thread when it is done.

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Fahir · Oct 12, 2020 at 07:38 AM 0

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So that basically means that no matter how many ms it is saying that Semaphore.WaitForSignal takes it actually doesn't take that time at all? Even on a real device?

Because I have the same issue. I managed to get my draw calls down to 26, I am allocating a few bytes of gc alloc every few frames but the semaphore thing takes 27.17 ms out of $$anonymous$$e 48.18 total time

sj631 · Apr 19, 2021 at 09:55 AM 0

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https://docs.unity3d.com/2020.3/Documentation/Manual/profiler-markers.html

Answer 2

Answer by sereschkin · Aug 31, 2021 at 10:13 PM

Just in case anyone is stumbling upon this issue in Sep. 2021 (Like I do, lol) and is sitting on a Mac: In my case I just switched to opengl, restarted IDE, switched back to Metal and restarted IDE again and now everything is so fast. Used Unity for months and never knew that this Editor can actually run fast.

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hawken · May 23 at 12:17 PM 0

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wow, everything is much faster now, thanks!

Answer 3

Answer by DanjelRicci · Oct 12, 2020 at 09:39 AM

In my case I literally just had to close the Logcat tab. It was causing these spikes every few moments, but it only happened in the editor.

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Semaphore Wait for signal accounts for 80% of total cpu usage.

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