Issue with low FPS while CPU/GPU usage is also low.

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sgtwisky
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Joined: 02 Aug 2017, 03:14

Issue with low FPS while CPU/GPU usage is also low.

Post by sgtwisky »

Hi everyone. Installed OpwnMW 0.42.0 (first version I have installed) and encountered an odd issue. After testing out OpenMW I went and added mods, and my FPS dropped massively. I went on the hunt for the cause, and it turns out it was Morrowind Rebuilt. Normally I would chock it up to my computer not being up to the task but I noticed something odd. While my frame rate dropped to around 20-25 MSI Afterburner Reported my CPU and GPU usage to only be around 22%. I also double checked just to make sure that my thermals were normal and they were all below 50c.

So is OpwnMW not using my hardware properly or is MSI Afterburner reporting my CPU/GPU usage wrong and my PC just cant handle Morrowind Rebirth?

Images:

http://i1337.photobucket.com/albums/o67 ... lrnhlv.png

http://i1337.photobucket.com/albums/o67 ... j5czij.png

I also noticed that while standing right in front of the door (second picture) to the Census and Excise Office that my FPS remained low. I am going to assume this has to do with the CPU/GPU being instructed to draw everything within the draw distance without regard to weather or not the player can actually see it or not. If this is the case, fixing this could have a good boost in performance for the entire engine. Though I could always be VERY wrong as I have no idea what is going on with the code.

System Specs:
CPU: AMD FX-8350 Black Edition (8 Core CPU)
GPU: AMD R9 270x
RAM: 16 GB
OS: Windows 7 Premium 64bit
OpenMW Ver. 0.42.0 (64bit)
OpenMW, Morrowind, and Mods all installed on an SSD.

EDIT: Just in case its important I am not using distant terrain. Just max default view distance.
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akortunov
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Re: Issue with low FPS while CPU/GPU usage is also low.

Post by akortunov »

OpwnMW not using my hardware properly
OpenMW now can fully utilize only two CPU threads.

I can not open your screenshorts, so if you hit F3 twice, which section have a higher value? Physics, GPU or scripting?
Also please, post your settings.cfg and console output (or openmw.log).

Typical causes of slowdown with mods:
1. A high number of new NPCs - IIRC physics is calculated in main thread for now.
2. Bad-designed scripts
3. A lot of high-quality sounds - player can increase a sound buffer soze in this case
4. A lot of unoptimized meshes.
sgtwisky
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Re: Issue with low FPS while CPU/GPU usage is also low.

Post by sgtwisky »

Draw / GPU is what seems to be high.
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akortunov
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Re: Issue with low FPS while CPU/GPU usage is also low.

Post by akortunov »

Morrowind Rebuilt
Tamriel Rebuilt or Morrowind Rebirth?
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scrawl
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Re: Issue with low FPS while CPU/GPU usage is also low.

Post by scrawl »

I also noticed that while standing right in front of the door (second picture) to the Census and Excise Office that my FPS remained low. I am going to assume this has to do with the CPU/GPU being instructed to draw everything within the draw distance without regard to weather or not the player can actually see it or not. If this is the case, fixing this could have a good boost in performance for the entire engine.
The word you're looking for is occlusion culling. Occlusion culling can be a good strategy, but most implementations will require the game data to specify some meshes that "occlude" things beforehand. Occlusing culling can also reduce performance in some cases (i.e. the worst case when nothing is obstructed), or lead to pop-in glitches caused by occlusion tasks on the GPU running a frame behind. I see it as a possibility in the future, but rather hard to do and definitely not a "magic bullet".
With interiors, some kind of portal-based CPU culling will probably do much better (i.e. using doors as portals between rooms, so that we can skip rendering a distant room whenever its portal (door) is not visible on screen, and even if it is visible we can use the visible section of the door to further cull the insides). We would probably need to define the zones in the editor first, though.
sgtwisky
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Joined: 02 Aug 2017, 03:14

Re: Issue with low FPS while CPU/GPU usage is also low.

Post by sgtwisky »

akortunov wrote: 02 Aug 2017, 06:30
Morrowind Rebuilt
Tamriel Rebuilt or Morrowind Rebirth?
Morrowind Rebirth. Although I was originally planning to run both I found that Rebirth was having issues. I can accept if my PC just isn't up to the task, but figured that if Afterburner is correct about the low CPU/GPU (more likely GPU) usage, then maybe it wasn't just me, but rather a bug of some kind.
scrawl wrote: 02 Aug 2017, 11:48 The word you're looking for is occlusion culling. Occlusion culling can be a good strategy, but most implementations will require the game data to specify some meshes that "occlude" things beforehand. Occlusing culling can also reduce performance in some cases (i.e. the worst case when nothing is obstructed), or lead to pop-in glitches caused by occlusion tasks on the GPU running a frame behind. I see it as a possibility in the future, but rather hard to do and definitely not a "magic bullet".
With interiors, some kind of portal-based CPU culling will probably do much better (i.e. using doors as portals between rooms, so that we can skip rendering a distant room whenever its portal (door) is not visible on screen, and even if it is visible we can use the visible section of the door to further cull the insides). We would probably need to define the zones in the editor first, though.
Ah thanks for the info. Never really understood how it worked. Just knew in some games it worked. Most of the info I did have came from some very basic C++ (Just windows console programs) and early access games I follow.

Seeing that your the one to ask Scrawl, any idea why the GPU might show low usage while also pumping out low FPS? or am I just crazy? lol.
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akortunov
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Re: Issue with low FPS while CPU/GPU usage is also low.

Post by akortunov »

Just tested a Morrowind Rebirth on a laptop with GT640M videocard.
There is a framedrop indeed (MR adds a lot of new objects). OpenMW profilier (F3) shows a high GPU usage and phycics.
Two of eight CPU threads have near 100% load, six threads are almost unused.

You can try to disable a water shader (it uses a lot of PC resources), but I am not sure if we can tweak the physics yet.
sgtwisky
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Joined: 02 Aug 2017, 03:14

Re: Issue with low FPS while CPU/GPU usage is also low.

Post by sgtwisky »

akortunov wrote: 02 Aug 2017, 18:22 Just tested a Morrowind Rebirth on a laptop with GT640M videocard.
There is a framedrop indeed (MR adds a lot of new objects). OpenMW profilier (F3) shows a high GPU usage and phycics.
Two of eight CPU threads have near 100% load, six threads are almost unused.

You can try to disable a water shader (it uses a lot of PC resources), but I am not sure if we can tweak the physics yet.
Water Shader does next to nothing for my FPS. I am more concerned that my GPU is only running at ~25% when the fps drop happens. Generally when I get an FPS drop its because my GPU is maxed out and cannot keep up. In this case its odd because it shows its not maxed out.

I will just be happy running the game without Morrowind Rebirth, I just worried that OpenMW may/may not be using a video card to its potential. Going to run some tests using GPU-Z latter to see if it reports the same thing as Afterburner just so I know I'm not crazy lol.
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Frik
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Re: Issue with low FPS while CPU/GPU usage is also low.

Post by Frik »

Scrawl recommended some tweaks to get better performance starting with posts located here. It seems that in many cases, the bottleneck isn't the GPU, it's actually the CPU speed. I get better performance from a dual core 4.2ghz CPU than I do from quad core 2.6ghz CPU.

Even though a mod is listed as compatible, it doesn't necessarily mean it's going to be efficient and run smoothly. Many of the full overhaul mods I've tested have caused big performance hits, with the exception being "Vibrant Morrowind", which is basically improved meshes and textures. You might be better off picking an choosing individual graphics enhancement mods and see how each affects your performance.
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psi29a
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Re: Issue with low FPS while CPU/GPU usage is also low.

Post by psi29a »

I'm going to go out on a limb here and say that the physics thread is maxing out on CPU, the result of which is causing FPS drop. Your GPU is starving for content update that is being delayed by physics trying to calculate everything. We had this with the slave cages with their odd and many collision shapes.

I think there is still some work to be done here.

So yes, a stronger (higher clocked) CPU will do better than a multi-core CPU with a lower clock.
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