I know this is a old thread but this saves me some time so I wanted to share it. Instead of setting the osi.exe each time I play the game I use this little program that permanently stores the priority settings in windows 10 so that osi.exe always starts in 'realtime' for me. You can choose 'high' as well. It's very easy, just like the task manager except you set it once and your done.
http://systemexplorer.net/
Thanks!