Shaders loaded slow for the first time.

Hi,
I used the streaming level in my project, but i find out that it will be very slow when loading other levels on iPad Air2.(using metal)
I used the profile to record what causes this.

After check the code I found this code takes most of the time.This newRenderPipelineStateWithDescriptor is a synchronous function and there is a asynchronous version of it, Can we use the asynchronous version to slove this problem?