CPU Usage up, GPU usage down results in worse performance.

[Ray Proudfoot]

Has anyone noticed that 5.2 appears to be hitting CPU1 harder than 5.1 did?

I monitor it via RTSS and it’s frequently hitting 100% even when airborne at altitude. That was at FL290 SE of London enroute to Brussels in the PMDG738. I’m struggling to work out what’s demanding so much CPU power. The GPU was no higher than mid 30s with clear skies.

I do run AIG Ai but use FSUIPC to limit aircraft to maintain 30fps. Same settings as I can remember as 5.1.

I’ve just spent a couple of hours taxiing around various airports I know are quite demanding of VRAM such as PILOT’s LEAL and VRAM usage is definitely down but RAM usage is significantly up. Hitting 15.7GB at several large airports with plenty of Ai. Previously it topped around 13Gb.

If that’s the case I wish LM had been open about it because I probably wouldn’t have gone to 5.2 knowing how things would pan out.

My somewhat modest 1080Ti is being used far less and my CPU is being driven quite a bit harder. This seems like a retrograde step for those of us with plenty of VRAM. Disappointing update and this is the first time I’ve said that about P3D.

If possible, some type of slider control to balance the CPU/GPU workload would be helpful. Otherwise I’m seriously considering going back to v5.1.

[Saldo]

Here it is the same : more load on the CPU and not even 2/3 load on the GPU compared to v5.1.

My 3090 is overkill now ….

[Wise87]

Here it is the same : more load on the CPU and not even 2/3 load on the GPU compared to v5.1.

My 3090 is overkill now ….

Same. I like to see more of the load put back on the GPU.

[Ray Proudfoot]

With others experiencing the same problem as me it confirms my suspicions. I can understand why this change was made if some graphics cards are running out of memory.

But my 11Gb 1080Ti has never got close to this and the 24Gb 3090 never will. Perhaps only switch processing to the CPU if the GPU is close to running out of VRAM.

[Saldo]

With others experiencing the same problem as me it confirms my suspicions. I can understand why this change was made if some graphics cards are running out of memory.

But my 11Gb 1080Ti has never got close to this and the 24Gb 3090 never will. Perhaps only switch processing to the CPU if the GPU is close to running out of VRAM.

As we already have a Texture Streaming feature there is no need for taking away GPU load and put it on the CPU again…

Imho the correct way to go is put even more load on the GPU and give the CPU main thread more breathing space for better performance….

[Airbumps]

I'm seeing my 5800X average around 70-80% flying in cruise in the FL's with the PMDG 777. I presume thats from texture loading etc with a reasonable hit on all cores - although like Ray says core 0 is almost always at 100%. I'm happy to see more cores being utilised, as long as they're being utilised effectively.

For what its worth my 3090 runs around 50% in the cruise depending on cloud levels....would be happy to move more off he CPU and put it into the GPU please LM.

[Ray Proudfoot]

I've run some tests this morning changing only two settings - Scenery Complexity and Building Autogen. I changed each from Extremely Dense to Very Sparse and noted GPU and CPU values.

As I can't post images here the topic is on AvSim and you can see it here. https://www.avsim.com/forums/topic/6017 ... nt=4551767.

[Martyson]

@ Ray Proudfoot

How to Post Screenshots (by Chris Metel):
https://www.prepar3d.com/forum/viewtopi ... 98#p238598

[Ray Proudfoot]

Here are the results of my test this morning.







I reduced all scenery settings to Dense and flew from London City to Heathrow. It was a stuttery mess with CPU1 locked at 100% but GPU no higher than 30%. More processing needs putting back on the GPU please.

[Ray Proudfoot]

I conducted the same test but this time without AIG Ai aircraft injected into the sim. CPU1 load was mainly in the high 80s / low 90s but where's the fun when you're the only aircraft in the skies?

The imbalance between CPU and GPU remains concerning. Using just 32% of the GPU in demanding areas doesn't seem right.

[Saldo]

Thank you Ray for your thoroughly testing several scenarios.
I agree with you that we need our V5.1 HF1 performance back.
Already we have a Texture Streaming feature where several GPU load is ported over to the CPU.

And with every release we should have more load shifting towards the GPU. Then P3D would be ready for the future.

[Ray Proudfoot]

Out of curiosity I lowered many of the scenery settings to zero and flew a Carenado PC12 from EGLC (London City) to EGLL (Heathrow).

Despite the lack of scenery to process CPU1 remained in the high 80s / low 90s and occasionally hit 100%. The only objects of any significance within 80nm were AIG Ai aircraft but given the fps stayed at 30 there wasn't a huge demand on the system.



It would be helpful if L-M could advise if they've shifted processing from the GPU to the CPU and whether they plan to redress the balance. There seems little point in buying expensive graphics cards as things stand. My 1080Ti is only supplying 32% of what it's capable of. More powerful cards will be used even less.

I appreciate I'm using AIG aircraft but these are 64-bit optimised and have never been a problem before.

[Clifton Crane]

Hello,

Thank you for the reports. To help us better identify the cause of the issue, could you try disabling Adaptive SimGroups in your Prepar3D.cfg and post your findings regarding CPU usage?

Code: Select all

[SIM]
AdaptiveSimGroupEnable=False

When enabled, AI objects within distance and speed thresholds will simulate at the same rate as the user object. This is done to reduce jitter when in formation flight with AI objects or multiplayer players. Disabling this setting will leave AI objects at their predefined simulation rates.

Can you also post your V-sync and frame rate limiter settings? Are you framerate locking internally using Prepar3D settings or are you using external software to framerate lock? Are you using internal settings or external software to control V-sync?

Regards,
Clifton

[krich]

In my circumstances, I am not using any AI traffic at all so I can report no difference with setting AdaptiveSimGroupEnable=False.

I have tried V-sync enabled/disabled in P3D, TB on/off with no external limiters. I have also tried RTSS scanline sync and a simple FPS limiter using RTSS whilst simultaneously having V-sync enabled/disabled in P3D (again, TB on/off both tried). Lastly I have tried Radeon Chill and setting maximum/minimum FPS to 30 in the AMD drivers.

Apart from the last combo of using Radeon Chill, Core 0 is always pegged to 100% - this was the same as 5.1. The other cores are however now regularly also being pegged at 100% irrespective of settings. As Ray's example also shows, even turning all the sliders to the full left is still creating 100% load on all cores.

The behaviour I am noticing compared to 5.1 is that whatever 5.2 is loading the cores with is much more intensive - so, even if I was seeing cores going to 100% in 5.1, they would run at 75 degrees Celsius - the same usage in 5.2 is causing the cores to run at 100 degrees Celsius and throttle.

[Martyson]

In my circumstances, I am not using any AI traffic at all so I can report no difference with setting AdaptiveSimGroupEnable=False.

I have tried V-sync enabled/disabled in P3D, TB on/off with no external limiters. I have also tried RTSS scanline sync and a simple FPS limiter using RTSS whilst simultaneously having V-sync enabled/disabled in P3D (again, TB on/off both tried). Lastly I have tried Radeon Chill and setting maximum/minimum FPS to 30 in the AMD drivers.

Apart from the last combo of using Radeon Chill, Core 0 is always pegged to 100% - this was the same as 5.1. The other cores are however now regularly also being pegged at 100% irrespective of settings. As Ray's example also shows, even turning all the sliders to the full left is still creating 100% load on all cores.

The behaviour I am noticing compared to 5.1 is that whatever 5.2 is loading the cores with is much more intensive - so, even if I was seeing cores going to 100% in 5.1, they would run at 75 degrees Celsius - the same usage in 5.2 is causing the cores to run at 100 degrees Celsius and throttle.

@ krich ,
"The other cores are however now regularly also being pegged at 100% irrespective of settings"

Just load the P3D default flight.
Nothing else running (weather program etc.)
Can you look at your cores usage with Taskmanager and do a screenshot?