A question on CPU performance

[silverheels2]

Hi all:

I am asking this question and I fully expect there may be no definitive answer, but here it goes anyway.

 

When running FSX I often look at CPU performance on CPU-Z and the task manager display. So the heart of my question is why does CPU performance peak at 70-80% when my frame rate has dropped below the ceiling of 30/sec? Why isn't the additional 20% being used? A good example is flying a VC payware aircraft into LGA on short final with Aerosoft Manhattan, freeware LGA upgrade, and my frames are down to 10-13 with CPU at 78%. My GPU is hardly drawing a deep breath at the same time. Here are the details:

 

System:

Intel Core i7-4820K 3.7GHz running at 4.5 with hyperthreading disabled

GPU NVidia GTX Titan

16 gig memory

FSX installed on separate drive from Windows

Win 7 Professional 64 bit

40 inch HDTV 1080 P

Resolution 1920 x 1080

 

Tweaks

Fiber frame .10

Bufferpools=0

Frames limited in FSX at 30

That other thingy which escapes me at the moment set at 14

Max radius set at 9.5

Min radius also at 9.5

 

Sliders

Maxed, except

Water detail at 2.x low

Autogen at very high

Traffic at 80% aircraft, 50% cars and trucks, 10% boats

 

Inspector set at FSX profile

 

Running ASN, REX, UT, GE, UT2

 

Any thoughts?

Thanks‎

[n55]

Spend some time reading the long article by NickN on settings. It is generally suggested that you not limit framerates, but leave them Unlimited. Some of the delay is caused by the loading of scenery from a HD while the CPU/GPU wait for the input. I run my 4790K at 4.8GHz with a GTX 970 4GB card superclocked and still get an occasional stumble as scenery loads from a 4TB drive with 64GB of RAM cache. There's a lot of stuff to handle with all of your add-ons, and I suspect scenery loading is the reason.

[silverheels2]

Spend some time reading the long article by NickN on settings. It is generally suggested that you not limit framerates, but leave them Unlimited. Some of the delay is caused by the loading of scenery from a HD while the CPU/GPU wait for the input. I run my 4790K at 4.8GHz with a GTX 970 4GB card superclocked and still get an occasional stumble as scenery loads from a 4TB drive with 64GB of RAM cache. There's a lot of stuff to handle with all of your add-ons, and I suspect scenery loading is the reason.

 

 

Thanks for your thoughts. I'll go and dig out the article. I did try unlimited frames once before and yes I did see an increase in frames but I also introduced stuttering where I had not seen it previously.

[alaskancrab]

In order for a CPU to reach 100% efficiency it needs to make just about ever data access from the onboard cache. Anytime you have to go fetch information from RAM you basically stall the processor. This is why i5/i7 are so great, they can keep the cache fed a lot better than AMD chips. It's one of the big reason console games run much better than on PC, a lot of attention is paid to not starving the beast and at the same time feeding it a healthy amount of data.

 

Also true for the GPU. If you keep running out of video memory that's when the stutters start and you end up losing frames rather quickly. It's better to be conservative than to try and find the tipping point in a game like FSX.

[loki]

As FSX can't make full use of all cores on multi-core processors, certainly not all of the time, CPU activity will almost always be somewhat less that 100%. One core is usually running at or near to 100%, while the others will fluctuate. If the sim is loading scenery and/or terrain data the additional cores will be busy, and when the sim isn't, those cores won't be.

[silverheels2]

Thanks all for your thoughts. Now I understand much better why my CPU seems to be running under 100%.

But now, given those facts, why is a faster CPU better? Since it can't possibly run at 100% efficiency.

[copperpen]

Because it can process the data faster.

[loki]

Thanks all for your thoughts. Now I understand much better why my CPU seems to be running under 100%.

But now, given those facts, why is a faster CPU better? Since it can't possibly run at 100% efficiency.

 

Faster is better as most of the simulation work is handled by only one core. The faster this core runs, the better the sim will perform. Even though it's an old engine at this point and doesn't make full use of modern CPUs, it does still benefit from core speed.

[evm]

This actually is a very difficult question. First of all it depends on how the CPU load percentage is calculated. simple caveat to illustrate why this is a problem: if the CPU is at 100% load, who is calculating the percentage graph and with what resources is it done? The CPU load is a tricky piece of data, especially in multi threading environments. In your case, the CPU has more processing power available than is needed, it is simply waiting on some bottleneck process or device to finish before it can proceed. Even if multithreaded and processed in parallel, the resulting frame has to contain all the results at the same time. So if anything running in a parallel thread is taking longer than the others (HDD comes to mind) your CPU gets bored.

 

The number is not a measure of efficency, but of load, and 100% is not a good thing actually. It would mean your CPU is struggling to keep up with the task your throw at it. That you are still experiencing low FPS is to be expected, FSX (in fact, the whole PC) isn't really developped for parallel processing, and has many bottlenecks built in.

 

First thing to do would be going SSD with FSX, maybe even RAMdisk if you can afford it. Then try to find out if you have certain features activated in FSX that your system really doesn't like, for example the SSAA setting in clouds can be tough on the GPU but not the CPU. Make sure nothing else is running, that could hold up FSX, like virus scanners or even monitoring tools.

 

The CPUs have not been inherently faster for some years now, like they used to 15 years ago. The semiconductor technology can't be taken any further (with a reasonable effort) when it comes to clock speeds. What we are getting are ever more complex CPUs (and OSs) instead, that try to do the "everyday jobs" in parallel or in optimized micro code on the CPU itself, so that we have a faster experience. But when you are dealing with complex software, you have to specifically build it for multiprocessing, or it will never be able to make full use of it. And FSX most definitely is not. So if it insists on doing something in sequence, in the worst case it could take just as long as on a Pentium of the stone age. But your modern CPU is bored by it anyway and shows low load percentage while you wait..

[silverheels2]

This actually is a very difficult question. First of all it depends on how the CPU load percentage is calculated. simple caveat to illustrate why this is a problem: if the CPU is at 100% load, who is calculating the percentage graph and with what resources is it done? The CPU load is a tricky piece of data, especially in multi threading environments. In your case, the CPU has more processing power available than is needed, it is simply waiting on some bottleneck process or device to finish before it can proceed. Even if multithreaded and processed in parallel, the resulting frame has to contain all the results at the same time. So if anything running in a parallel thread is taking longer than the others (HDD comes to mind) your CPU gets bored.

 

The number is not a measure of efficency, but of load, and 100% is not a good thing actually. It would mean your CPU is struggling to keep up with the task your throw at it. That you are still experiencing low FPS is to be expected, FSX (in fact, the whole PC) isn't really developped for parallel processing, and has many bottlenecks built in.

 

First thing to do would be going SSD with FSX, maybe even RAMdisk if you can afford it. Then try to find out if you have certain features activated in FSX that your system really doesn't like, for example the SSAA setting in clouds can be tough on the GPU but not the CPU. Make sure nothing else is running, that could hold up FSX, like virus scanners or even monitoring tools.

 

The CPUs have not been inherently faster for some years now, like they used to 15 years ago. The semiconductor technology can't be taken any further (with a reasonable effort) when it comes to clock speeds. What we are getting are ever more complex CPUs (and OSs) instead, that try to do the "everyday jobs" in parallel or in optimized micro code on the CPU itself, so that we have a faster experience. But when you are dealing with complex software, you have to specifically build it for multiprocessing, or it will never be able to make full use of it. And FSX most definitely is not. So if it insists on doing something in sequence, in the worst case it could take just as long as on a Pentium of the stone age. But your modern CPU is bored by it anyway and shows low load percentage while you wait..

 

Thank you for this excellent and understandable analysis. You touch at the heart of why I asked the question. It is this: my system has quite a bit of power between the I7 CPU and the GTX Titan. What I am wondering is have I configured my system with tweaks etc so there is a proper balance between the CPU power and the GPU power? Maybe "proper" is the wrong word. I'm looking for an effective balance between the two as measured by FSX performance, as measured by frames as I approach LGA RW 4. What do you think of that?

[silverheels2]

Because it can process the data faster.

 

OK. I understand that.

Thanks

[evm]

The NewYork area is a tough one. All those buildings and the autogen take their sweet time to get drawn. My guess is, that the autogen process in FSX is especially slow, not able to take advantage of multithreading at all. It probably isn't that heavy a task, but slow nevertheless (like, reading from the disk, calculating, then reading again, calculate and so on.) I even read some post that in this particular area FSX is always slow, sliders min or not. Never tried that myself.

 

Try out the extremes, like 100% buildings, no buildings at all, completely overcast, not a cloud, etc and document the results until you can classify the probable caus(es).

 

Are you running DX10?

[silverheels2]

The NewYork area is a tough one. All those buildings and the autogen take their sweet time to get drawn. My guess is, that the autogen process in FSX is especially slow, not able to take advantage of multithreading at all. It probably isn't that heavy a task, but slow nevertheless (like, reading from the disk, calculating, then reading again, calculate and so on.) I even read some post that in this particular area FSX is always slow, sliders min or not. Never tried that myself.

 

Try out the extremes, like 100% buildings, no buildings at all, completely overcast, not a cloud, etc and document the results until you can classify the probable caus(es).

 

Are you running DX10?

 

No, not running DX10. The way I typically operate is that flying to small cities or the Caribbean I use FSX and PMDG or IFLY 737NG. They perform well with my settings even with add-on scenery so long as stay away from NYC, Miami, LAX, and so forth. More due to OOM threats rather than frame loss so much. Then I use my fully loaded FS 9 with IFLY 737 to go to those crowded places and it runs super on my rig. Set at 30 frames, I rarely see less than 22 to 24 even in the most dense FS 9 areas. I started this thread to get ideas on how to think about putting more load in FSX on the Titan which seems to be loafing along, and the CPU which is breathing hard. Are their tweaks or settings which make the GPU work harder is my question. I like your idea of taking away eye candy one at a time to see what is the biggest drain. As I mentioned earlier I run everything in FSX at pretty much full up except autogen at very dense, air traffic at 80%, cars and trucks at 50% (which is plenty to get the feel), and boats at 10%. Btw, there is a great tweaker out there which shows how to slow down the cars and trucks so they look right. I installed it and it makes a huge difference. Now when I'm on a takeoff roll and look over at the road, the trailer trucks are not blowing by me like I'm stopped :)

Thanks for your thoughts.