Extreme GPU spikes from ParticleSystem

We are experiencing extreme GPU spikes in Unity 2019.2.0f1 on the first time a ParticleSystem is played (as shown in the screenshots below), and have been unable to figure out the cause. We don't really know where to go from here, so any help would be greatly appreciated.

The spike seems to reliably happen on the FIRST time a ParticleSystem with these materials is played (and not subsequent times), so we thought that perhaps the shader used by the ParticleSystem wasn't being preloaded. With that in mind, we tried the following things, but unfortunately saw no change in behaviour:

• Adding the shader (Legacy Shaders/Particles/Additive) to the preloaded ShaderVariantCollection
• Adding the shader to the "Always Included Shaders" list
• Calling Shader.WarmupAllShaders() after loading the scene

I have also stepped through the game with the Frame Debugger and saw no significant change in GPU calls occur when the ParticleSystem plays. The spike isn't exclusive to the editor either; it also happens in a standalone build, causing the game to stutter.

Would greatly appreciate some guidance here. Thanks!

Spike in profiler:


GPU usage hierarchy during the spike:
(note that is it not always DrawInstanced that is the culprit - it randomly sometimes is DrawStatic)


CPU usage hierarchy during the spike:


ParticleSystem materials:

 

Anyone have any ideas? Hard to find information on this kind of performance issue.

 

Thanks Martin, I did that and it seemed to resolve this issue.

(For anyone else reading this thread in the future, I used the technique described here: https://ralphbarbagallo.com/2012/07...kes-in-unity3d-when-a-model-is-first-visible/ )