FH3 stuttering cause found
I've done some investigation. From what I've read on the forums, measured in MSI Afterburner and found on the disk:
The reason of those stutters is the fact that the game uses EFS which consumes a lot of CPU.
Yesterday, i've captured a usage on my CPU and GPU, and found interesting thing, when CPU has 100% a lot of stuttering appears and GPU usage lower fluctuates at 50-80%. Stutters mostly appears in a city and mostly at the fast speed, when the game loads a lot of assets simultaneously. The i've navigated to a folder where game is installed and found that game folder uses EFS, which AFAIK uses AES256 encryption. Having EFS is ok for sensible documents, not the game files, because it requires a lot of CPU to decrypt.
There's also a post on the official forums where a user has issues on a 4-core CPU, and has no issues on a 6-core one.
P.S. My specs are i5-6600k @ 4.0GHz, MSI Gaming X GTX 1070, 16Gb RAM, installed on a 512Gb Crucial MX100.
Update 1 During cpu spikes there's a high IO activity too, as assumed on the mentioned forum thread, this can be the result of encryption preventing files to be cached. This can also prove, the encryption might be a problem, because cpu is bottlenecked when reading a huge amount of data. If you have HDD, then read speed is pretty low, meaning you have less data to decrypt each second, but on an ssd, data reads very fast resulting in a big cpu spikes
So a possible solution for SSD users is to put you game to HDD or to slowdown you ssd. Not working :(