Identifying the bottleneck(s)

Harry Voyager · October 17, 2019

For background, I'm id'ing the bottlenecks in my current build and trying to get a ballpark idea just how much more CPU I really need to throw at the problem at hand.

The system in question is this:

PCPartPicker Part List

Type	Item	Price
CPU	Intel Core i7-4770K 3.5 GHz Quad-Core Processor	$335.98 @ Amazon
CPU Cooler	Corsair H110 94 CFM Liquid CPU Cooler	$574.98 @ Amazon
Motherboard	Asus Z87-Pro ATX LGA1150 Motherboard
Memory	G.Skill Ripjaws X Series 32 GB (4 x 8 GB) DDR3-1600 Memory	$149.99 @ Newegg
Storage	Samsung 850 Pro Series 1 TB 2.5" Solid State Drive	$579.99 @ Amazon
Storage	Western Digital Caviar Black 1 TB 3.5" 7200RPM Internal Hard Drive	$49.49 @ Amazon
Storage	Western Digital Caviar Black 1 TB 3.5" 7200RPM Internal Hard Drive	$49.49 @ Amazon
Storage	Western Digital Caviar Black 1 TB 3.5" 7200RPM Internal Hard Drive	$49.49 @ Amazon
Video Card	Gigabyte GeForce GTX 1080 Ti 11 GB Founders Edition Video Card	$1259.00 @ Amazon
Power Supply	OCZ ZX 1250 W 80+ Gold Certified Fully Modular ATX Power Supply
Optical Drive	Lite-On IHBS112-04 Blu-Ray/DVD/CD Writer
Operating System	Microsoft Windows 10 Pro OEM 64-bit	Purchased For $0.00
Sound Card	Asus Xonar Essence STX 24-bit 192 kHz Sound Card
Headphones	Beyerdynamic MMX 300 Headset
	Prices include shipping, taxes, rebates, and discounts
	Total	$3048.41
	Generated by PCPartPicker 2019-10-17 00:48 EDT-0400

The question is, do I look go to a 5.0Ghz Intel 8 core, or do I target rebuilding it with a Ryzen 3800X. My primary games are Il-2 Great Battles, and DCS: F-14, both in VR. Il-2 just added multi-threading support to enable extended ground object view range. Il-2, at least, does use AVX instructions. The headset I'm currently using using is an Occulus Rift CV1, though after this I'd like to upgrade to something in the HP Reverb range. Honestly I'd really like to be able to drive something like a Pimax 8KX, but I'm thinking driving that many pixels at 45hz is not going to be achievable with hardware available for the foreseeable future.

The test results are a simple 8v8 air battle over the Stalingrad map, with each team having 4x single seat fighters and 4x twin engine multi-crew bombers. The curious pat of the results are that, while the GPU was running at about 62%, the CPU was running at ~50% on eight threads. This brings up some interesting questions: I'd understood the game to be single thread limited, but, at least on this CPU, that does not appear to be the case. I'm also surprised by how no CPU hit 100%. I'm wondering if this is an artifact of hyperthreading as implemented on the Haswell architecture. All of this got a max frame rate of 45 fps, with an average framerate of about 27fps, and a 1% low of 24fps.

The implication to me is that Il-2 may now be much more amiable to multi-threading, though I still do not know if it can gainfully take advantage of more than 8 threads. This also tells me I need to at least, double my CPU horsepower to get up to 45 fps, and probably quadruple it if I want to get closer to 90 fps, regardless of the amount of GPU power required to drive it. One question here is, is there a good way, short of getting a new CPU to figure out how many threads Il-2 can now split the loads over?

Second thing to think about is how the Reverb will impact frame rates, once the CPU is removed. It would be going from 2.5 megapixels on the Rift CV1 to 9.3 mega pixels on the Reverb, but I'm not fully sure how that actually scales on this card. Thoughts?

Thank you,

Harry Voyager

HardwareMonitoring.hml

191x7 · October 17, 2019

I don't know how those simulators use resources, but I can tell you from general gaming and some multiplayer games like Battlefield V, there are titles where an older 4 core with HT does bottleneck a high end card like the 1080Ti.

Thus, I would recommend a modern 6-core or better, something like the Ryzen 5 2600 or 3600, and from Intel the 8600K or 9600K and up.

Harry Voyager · October 17, 2019

8 hours ago, 191x7 said:

I don't know how those simulators use resources, but I can tell you from general gaming and some multiplayer games like Battlefield V, there are titles where an older 4 core with HT does bottleneck a high end card like the 1080Ti.

Thus, I would recommend a modern 6-core or better, something like the Ryzen 5 2600 or 3600, and from Intel the 8600K or 9600K and up.

They tend to be computationally intensive. Recall, Havoc does not cover the sort of fluid dynamics type problems that you need to handle flight. And the resultant forces on each aircraft are going to involve significant vector math. What I don't know is if the effects they're doing are heavily summation or heavily multiplication driven.

I mean, we're getting. 27 fps with only 16 aircraft in the air, and the GPU is at barely half load. It's chewing a lot of numbers.

Now, what I just found out from the forums is that it tends to thread hop, so tonight I'm going to need to use perfmon to see if I can get a thread level measurement of the CPU usage.

Harry Voyager · October 18, 2019

Looks like the game generates around 60 threads, of which 2 threads are using 70% of the CPU time each, and another 6-7 that are using between 10-20% during flight.

So leave me in a bit of dilemma. On the one hand, this game now uses a ton of threads. On the other hand, only about two of them are critical path. So does that mean it's better to go purely for the best single thread performance, or will a certain degree of multi-threading prowess help keep the brush clear from the critical path threads?

Will have to see if AMD can get their Ryzens doing consistent 4.5-4.7 dual core boosts; would significantly simplify this conundrum...