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Game engine & Multi threading + performance degredation


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Hi Team,


Just some notes on some testing ive done with regards to multi threading & performance in this game (and some unusual results?)


I have been testing this on multiple different cpus (7700k, 8700k, 3900x, 3960x,) but ill use thw 3960x (threadripper) as my prime example..


In 24 core mode, the game will utilise 48 threads, FPS will sit around 40 with GPU use around 30% (2080ti)

In 12 core mode, it will utilise all 24 threads, fps will go up slightly to around 60 fps

in 6 core mode it will once again... utilise all 12 threads and FPS rockets all the way up to 120ish with the GPU now aorund 90%

If i manually set affinity via windows, and utilise only 3 cores.... (only 3 threads total) once again the FPS goes up. to around 130


3 cores does introduce some stuttering though, 4-6 threads seems to be the happiest point for the game...


What im getting at though, is if the games utilising all the threads, why does performance go down when adding more ?


Some people might say inter CCX latency on the threaripper, but ive tried all different combinations of affinity and thats made very little difference.

It would jsut seem the games putting load onto cores when it doesnt need to, and causing the game in turn to run slower ?


Any Devs have much of an insight into this ? or has anyone else noticed it ?


Also that being said for anyone using a high core count CPU, try disabling a few cores through task manager and see if your FPS jumps up !

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So as far as a 9700k, would 4 cores add performance? If so I forgot how to set multiple affinity, so how do I set 4 cores? I am at bloodmoon 28 right now and I have a lot of dynamic lights so the FPS is going down a bit now.


In windows task manager go to the details tab, find the program you want to set and right click then click Set affinity.



Tested on a Ryzen 5 2600X, turning off SMT generated about 10 FPS in a scene with 50 zombies, lots of torches and a few trees.


I wonder if this is a Unity3d issue.

It looks like Subnautica had a similar problem. This mod sets the CPU affinity to 3 cores and they claimed it doubled the FPS: https://www.nexusmods.com/subnautica...ab=description


There is probably a lot of information that needs to be shared between threads which could be creating a bottleneck.

I wonder if this would also affect dedicated servers with high core counts.


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