FPS is cut by 90% with Steam Overlay.
The difference between 730 and 300 fps isn't really that significant. That's a difference of ~2ms of frame render time. It makes sense that running Steam uses some GPU resources, in my opinion.
Consider that your monitor can only display 60 fps anyway, which takes 16 ms per frame. (8ms if you have a 120 Hz monitor). Anything over that is essentially wasted rendering effort. Especially since most physics/game simulations work at fixed framerates nowadays.
Horrible response, the difference between 300 and 730 is HUGE. It doesn't matter if there is no visual difference between 300 and 730 from a FPS counter. The fact is, it is still hurting a LOT. Why should Linux be satisfied with 300FPS with Steam running when I get 2000-3000FPS in Windows? If the framerate is effectively being cut in more than half, that would mean if I was playing a game that gave me 60FPS without Steam, I'd only have 20FPS with Steam running in the background.
I'll have to agree with ginquo's response. FPS is not an accurate measure of performance. Actual clock frame time as he indicated should be use as a metric. The benchmark industry have been perpetrating this erroneous myth for the longest of time. I guess for users its a viable metric, but as a developer absolute frame time is more important. When your allotted frame time is being overrun, one doesn't investigate whats taking up FPS, but what operation is taking up actual time ( seconds / milliseconds. ). However, you concern that something is amiss is a valid one, and unfortunately, I haven't ran Steam on Linux yet so I cannot comment on that. One difference however, could be in the drivers.
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