How to make the bundle load smoother?

Hello!

I load bundles through UNITY AssetBundleManager.
Bundles loading is async.
But in profiler I get one big spike when load bundle.

Average fps in webGL build is 60. But in spike fps sags to 15.

I want loading to be longer, but without big spikes.
(for example 4 spikes to 30fps instead 1 to 15fps)

Is it real?

I use Unity 2017.3 and webGL build.


(on image one awful big spike)

It's worth noting that I download small bundles witch loads for 0.05 - 0.5 seconds, but cause this spike.

 

So I tried LZMA, LZ4 and uncompressed format.
(as I understand WWW.LoadFromCacheOrDownload in automatically understand compression format and I shouldn't change anything except bundles files)

And despite changing the compression format resulting is the same.
Results for both variants have big variance values. From 35 to 70 ms.

Bundle: 628kb compressed, 1,1mb uncompressed. Dependences = 0;

Result without compression

Result with compression



So Application.Preload assets take very much time. (also it depends on the size of bundle)

How to remove this big spike and get 35-40 guaranteed fps on bundle load?