https://steamcommunity.com/games/593110/announcements/detail/500576552635859540
(https://clan.akamai.steamstatic.com/images//27766192/3146e304691ad715b2583d423c90ad2d12bb1995.png)
This feature is designed to help you understand how your PC is performing and how it is impacting your game's performance.
The new performance overlay will show you frame rate values, similar to the old FPS counter, but it can also break out generated frames from DLSS or FSR vs actual game frame rate. It can show you min/max single frame values and a graph of frame rate over time. Additionally, it will show you CPU performance information, GPU performance information, and system memory usage information. These pieces of data can be useful to understand the causes of bad game performance whether that be a slow CPU, GPU, or too high graphics settings that are over subscribing your video or system ram.
The performance monitor can help you understand your frame rate (both including frame generation, and base game frame rate), and it can help you see if CPU utilization might be your bottleneck, or if your GPU is. You can see if you are out of system or video memory and if those factors are impacting performance as well. The performance monitor looks something like the below at full detail (detail levels, screen position, contrast/saturation, and background opacity are adjustable in Settings->In Game).
The Steam Performance monitor will detect frame generation technology and break down both the DLSS/FSR Frame Gen including FPS and the actual game FPS over 1 second intervals.
(https://clan.akamai.steamstatic.com/images//39983882/744844f333555af1f1a9b07e766747e1d64e3351.png)
https://help.steampowered.com/en/faqs/view/3462-CD4C-36BD-5767
Oh wow, that's pretty neat, actually.