Was just working on a project for most of the day, and then noticed later on that I was getting large spikes in the performance meter (average load) especially when starting playback from different points along the timeline. I had never had such spikes in Cubase8/8.5 before. I then loaded a few other projects in Cubase 9, only to find that the meter was running fine with no spikes. After returning to the original project as still getting the spikes again, I disabled all plugins, and the performance went back to normal. This seemed odd since most of these plugins (3rd party) were used in the other projects as well. The only plugin that was new to this project was the Frequency EQ that comes with the new Cubase 9. After disabling it, everything was fine again, even with the 3rd party plugins.
I tested on (2) internal drives and (2) OSX systems loaded with the exact same results. Upon further testing, I found that it has to do with when the Frequency EQ plugin is automated on tracks. If you either disable the Frequency EQ plugin, or disable the automation of it, everything is fine. Turn both the plugin(s)and their automation back on and performance meter starts piking again. The more instances of Frequency EQ plugin and automation you have on tracks in your session, the worse it seems to get.
Needless to say that all along I thought it might be one of my third party plugins. But for Cubase 9’s own EQ that comes with the program to be causing these issues is pretty bad. Hopefully since the program is fairly new, it will be worked out shortly.