Understanding "Total Frame Time"

[Parisio Riel]

I am trying to understand part of the statistics bar in regard to “Total Frame Time” and “Spare Time.” I am looking at the SL Wiki page on statistics It says under “Total Frame Time,” that <22ms is healthy and >22ms represents severe simulator load. Now, my stat box shows a Total Frame Time of 22.21, which sounds bad, if the Wiki is right. But I notice further down that I have a “Spare time” number of 20.774ms, and “Spare time” is not mentioned at all in the SL Wiki. I am wondering if the ”Spare Time” number should be subtracted from “Total Frame Time” to get a usable number for analysis. Btw, I notice the same situation on the Firestorm Wiki: Moreover, there I see an image of the Stat Bar which shows a Total Frame Time of 22.674, which leads me to believe my analysis above is correct, and that the Wiki texts are incorrect. Can someone enlighten me? Many thanks.

 

 

 

[Ohjiro Watanabe]

Yes, the wiki is out of date.

Spare time was added somewhere along the way and the wiki didn't get updated.

Total Frame Time should be around 22.222 ms because the frame rate is 45 and 1000ms/45 = 22.222 which is how long the server has to do its stuff to generate the frame.

If there is no free time it means that the server doesn't have time to do everything that it needs to do. That means you are going to get server lag. The other stats in that section tell you the cause.

[Madelaine McMasters]

Hi Parisio,

I'm wading out into the cattails here, as my understanding of SL internals isn't expansive. The fastest the servers will run an SL simulation is 45fps. That's 22.22.... ms per frame. (And that is different from and independent of your viewer's scene rendering rate.) So, if you're seeing that frame time, the simulator is being governed, just like an unloaded lawnmower engine, which doesn't cut any better at 10K rpm than at 3K. That's a good thing, meaning the server has more than enough ooomph to do 45fps. The "spare time" number you see indicates that the server actually has lots of spare time. You simply can't use it because 45fps is the speed limit and the reserve CPU horsepower can be better used by other regions sharing your server processor.

Once you start loading up the sim with things, the spare time will decline until there is none left. At that point, because the server must reserve horsepower for the other regions, it will decrease your sim's frame rate to hold your CPU usage constant. That's the point at which the frame time starts to rise, and you'll see zero spare time. This is the equivalent of watching your lawmower bog down when you run it into the cattails in the culvert.

Don't do that!

;-).

[Parisio Riel]

Many thanks to both of you. Very helpful replies.