Reducing CPU bottleneck?

[odai 4]

Hello

 

I recently built the following system and installed P3D v3 to use on it:

 

- Intel 6700K @4.4Ghz, HT enabled

- 16GB DDR4 @ 3GHz

- Both local drives are SATA3 SSDs

- EVGA GTX 1070 FTW (boosting to 2GHz in the sim)

 

P3D looks incredible in rural areas with little traffic or building-type scenery, running at a smooth frame rate when locked at 30FPS. However, if I try loading a flight starting at LHR (all default scenery apart from Orbx FTX Global and FS Global mesh), with traffic set at ~50% (MyTraffic X is installed), the frame rate plummets to 10 FPS.

 

All the settings are at the maximum and frame rate is locked at 30 FPS. I appreciate it's a bit of an ask to have all settings to the right, but I can see that with this set up it seems that the CPU (not the GPU) is the bottleneck. I see from the task manager that the one thread is stuck at 100% usage, while GPU usage hovers around 70%. When in rural areas and I don't have these performance issues, GPU usage shoots up to the high 90's and the usage on the main render thread on the CPU drops.

 

I did try putting all settings to minimum and one by one increasing back to where they were. My suspicions were confirmed, the vast majority of settings have no impact on FPS in the above detailed scenario. The only settings that I need at minimum to have acceptable frame rates are those corresponding to autogen and traffic. I can have everything to the right but disable traffic and/or autogen completely and get decent frame rates in urban areas like around LHR. As far as I can tell, these are the main CPU bound settings.

 

However, there is no good compromise as you would expect with these settings to get a decent frame rate while maintaining realism. With traffic at 50%, I have to completely disable autogen to get decent frame rates. Even at "minimum", autogen results in the frame rate dropping to ~10 FPS. Conversely, if I want a decent amount of autogen, I have to disable AI traffic.

 

The frustrating thing is, as was the case with FSX, CPU utilisation as a whole is quite poor (only around 50%), even with that one thread maxing out. Are there any mods that can improve CPU utilisation and therefore reduce the CPU bottleneck?

 

The really worrying thing is that both the future DTG Sim and P3D are heavily reliant on FSX code, so this problem (with its roots dating back to FSX's launch) could be an issue we need to deal with way into the future! 

 

Odai.

[RaptyrOne 1,398]

One thing that will increase your frame rate, move the frame rate limiter to Unlimited. It might give you good results in 'rural' areas but when the pressure is on the system, the frame rate limiter only makes it worse. For this reason I only use Unlimited.

[odai 4]

Thanks for the suggestion, unfortunately using 'unlimited' still only results in a frame rate of about 14 FPS. CPU still seems to be the bottleneck. 

[Michael Moe 494]

look at Robs guide at the top

 

http://www.avsim.com/topic/494633-prepar3d-guide/

 

Michael Moe

[ryanbatc 12,818]

Reduce your settings!

 

You simply can't run max settings!

 

Especially get rid of dynamic reflections

[odai 4]

Thanks for the input guys, but as I mentioned above the only settings that make any difference at all are the autogen scenery and traffic sliders. Everything else has zero impact, whether at maximum or minimum. And I have to either completely disable AI traffic or disable autogen to get decent frame rates.

 

I will look at the cfg mods that are listed but it is not too clear what will help with CPU bound performance issues.

[Manny 1,293]

Odai, your findings confirms with my setup and I have almost the identical system. including the 1070.

 

I had posted earlier that going from i7-3770K to i7-6700K did not do much good for me.. I still languish at 10FPS when I am flying near EGLL or KLAX

[kakusso 12]

I wish LM would enforce a policy where planes would do all their calculations outside P3D and only inject the results onto it like the Majestic does helping to reduce the core one bottleneck.

Core one works as if the software cannot abstract the physical layer. I wish the workload on core 1 could be shared between many physical or logical cores and that is not happening at the moment.

I wish someone would create a virtualization tool that would spread the load of core one across multiple cores, because the load is relatively low when considered globally.

The AI traffic should also be removed from core 1.

Why autogen has to be on core 1?

Poor core 1, so much load into it.

[DylanM 1,069]

You should also be running the AI Traffic Manager - should make a significant difference with that traffic density.

[Manny 1,293]

I wish LM would enforce a policy where planes would do all their calculations outside P3D and only inject the results onto it like the Majestic does helping to reduce the core one bottleneck.

 

I buy lots of Addons and some of them are so bad I do not use them after the first few min and yet I do not return them (like use the Flight 1's 30 day money back) on the account that this hobby is often supported by the "Starving programmers"  (That's my belief).  The only exception to that was, I returned the MAjestic Q300. The only add on I returned. 

 

Because they did everything outside, the basic  numbers like Attitude indicators and Turn Coordinators were not sent back into the sim. This made use of cockpit hardware invalid. I could not use my Home Cockpit gauges..e.g.. like Flight illusion gauges (Attitude indicator and Turn Coordinator) does not work

 

I like your idea and I support it with one caution that they need to be interfaced with the Sim itself and not go totally haywire.

[garrett_frank 150]

 

 

Why autogen has to be on core 1?

 

Call it an appeal to authority but I have to assume there is some reason why this is the case. But maybe not: X-Plane isn't so wildly CPU-bound. I think there are very few here and elsewhere that actually understand the ESP architecture enough to give us some salvation in terms of answers. I know I sure as hell don't have any...

[Mickeyj 35]

Just for info, the LHR area is besides SXF, KSEA, JFK, CDG etc one of the most demanding areas in P3D and FSX. So no wonder that your PC goes down to its knees. Either live with the poor performance or try to avoid those areas. I for myself choose to avoid it.

[sedacajr 17]

Try this:

 

- Reduce AI Traffic to 10%

- Use AI Traffic Manager

- Set road traffic to 0%

 

Let me know.

[james_2k 36]

on my pc, unlimited fps certainly gave better fps. but it greatly slowed the texture loading, meaning they wouldnt get fully sharp until i was on top of them!

[Kuragiman 227]

Until there is a new simulation platform that throws off the shackles of old dated tech and embraces fully today's DX11/DX12 cards, learns to actually use those multi-cores properly... I think it will always be a game of give and take.  You have to kill something off in your settings if you want that other thing, especially in heavy hitter simulations like PMDG that focuses so heavily on avionics reproduction that the CPU gets kicked around like a soccer ball and doesn't have a lot of time to play any other games in-between.

 

Maybe one day before I die.. I will get to see a sim with 4k textures, realistic draw distances, 100% AI traffic at airports ... maybe..> OR.. I could just go get a real pilot's license... XD  Might be cheaper in the end!