Does Hyperthreading reduce DCS performance?

I was wondering if Hyperthreading (2 threads per core) will decrease performance in DCS. Afaik DCS - including 2.5 - will only utilize 2 threads (one main and one for sound). Given that, I assume that having more than let's say 3 or 4 cores (1 or 2 additional cores than DCS requires might be needed for Windows background tasks).

So if one core needs to handle two threads instead of only one it should be slower in execution, right? Also having a higher single core frequency should be better than having more cores.

(Reason why I am asking are the recently annnounced Core i9 9900K with Hyperthreading and Core i7 9700K without)

Does anyone has tested this?

I ran with HT disabled for many years until recently. I enabled it again before the summer as DCS have started to utilize more threads. So no, HT does not reduce preformance but increases performance. At least on my rig.

DCS uses much more than 2 threads, but 4 cores are still enough. Over all, DCS uses only 25% on my six-core CPU. HT can lower perfomance if an application uses thread instead core(in 2 core processor 0 and 2 are cores and 1 and 3 are threads). So check affinity mask on a processor with HT.

Turn the Hyperthreading off, run DCS and check the CPU utilization. If at 100%, turn the Hyper on. You have to fill the physical cores before to fill the others. Hyperthreading improve the performance by 20% when all cores are used.

Don't know if i'm right,i think running an aircraft in DCS needs 2-3 cores.

Then, you have to addition more cores to run the objects depending on your appetite.

Does Hyperthreading reduce DCS performance?

HT is only useful on some compute tasks. intel added it for servers doing batch work loads. games, and in general, don’t have those types of tasks.

so HT will probably not improve your fps. it depends on the structure of the task and whether the virtual thread can utilize the same cache as the physical thread and make use of a shared bus.

also, if you overclock your cpu, you can achieve higher OC’s by turning HT off.

since most games need more Ghz, instead of more threads, there is an advantage in turning HT off and OC’ing your cpu.

I use process lasso to force DCS onto physical cores only. I’ve noticed it doesn’t change FPS whether on or off, but I get significantly more stuttering when I allow DCS to use logical cores (HT on)

With DCS I've never had any difference between HT on or off, in term of performance (fps) or stutters. Since 1.5 when I started having an eye on it, till now.

On other sim it can be critical, but with DCS and my settings, I've never had a difference.

Actually with DCS there are case when (with HT on) a logical core can be maxedout, limiting logically the performances, f.e in PG map, but I don't know if disabling HT improve things (I don't have PG map).

BTW talking about what logically happens with cpu usage and hyperthreading in actual DCS is tricky, as usage doesn't seem to behave logically because :

1) different features/technologies with different DCS maps so different behaviors

2) probably the engine is already evolving with vulkan use in aim, and what will be improvements when ready is actually doing weird things with cpu usage.

In comparaison DCS 2.5.0 was behaving logically, perfomances being capped by : 1) fps cap (manually defined, or vsync, or VR), 2) hardware usage when topping 99% with gpu or cpu 1 core/thread or even all cores (it was possible with 2.5.0)

Actually DCS can put gpu to 99% without trouble, but not cpu (even with gpu room and no fps cap, the cpu refuses to go max). But even with strange behavior the performances, to me, are really OK. And I guess the situation is under control by ED.

But it's actually hard to make definitive statements about cpu "settings" and performances. (even cpu clockspeed is not making difference when already enough "high")

Only advice I can point about cpu settings is AVX offset : don't use one because DCS uses AVX instructions (or system detects AVX instructuions when DCS is running) and cpu clockspeed decrease (according to how AVX offset is set, mine default is minus 400Mhz) with each instruction, so constantly...

The newer your Intel CPU is the less it seems to matter, it never bothered me tbh, from 2600k-6700k-7700k and now 8700k, I ran all of them with both setups, didnt change much.

What I think is beneficial, is leave HT on and use ProcessLasso once you run DCS + tons of other stuff like streaming, TiR, VR, music, and all those little gadgets we all have. But also, this never made a bad day sunny, it's polishing an already polished car. Some say PL fixed their stutter, that speaks for itself, it wont harm but maybe also wont gain any advantage, try it out, it's FREE, bitsum.com

I would watch the AVX advixce if you are into heavy overclocking. I dont run any AVX offset, not even at 5.2. It chews through all this without hiccups buut the temps go real high, ~85°C. But DCS will never ever get the CPU as hot as a full dose of prime95-AVX enabled

Does Hyperthreading reduce DCS performance?

let’s not get confused.

you only have a few physical cores that can do actual work.

pretending there is twice as many (HT) almost never results in better performance.

if it did, we could all just pretend there is 100 of them and run mega settings with mega detail at 140fps

DCS uses much more than 2 threads, but 4 cores are still enough. Over all, DCS uses only 25% on my six-core CPU. HT can lower perfomance if an application uses thread instead core(in 2 core processor 0 and 2 are cores and 1 and 3 are threads). So check affinity mask on a processor with HT.

Sorry, it doesn't use more than 2 threads, DCS is still a "dual-core" application. - Yes a key distinction is to say threads not cores. Because those two threads are bouncing around on many cores, as are all other applications, the terminology to say that something can use "more cores", "multiple cores" is fundamentlly wrong because any single threaded application can use multiple cores because that's how the CPU/Firmware/OS naturally manages all the workloads/applications to run all "simultaneously in real time". Thread Scheduling is by running one application for a bit and another for a bit, back and forth, so you get the illusion everything's running at the same time.

Because this is happening so fast, the common utilities such as Task Manager and others which show the CPU Core utilization without the context of what's really happening under the hood and I think it may even fooled the MS developers and others including the public that this is some kind of "load balancing" which I've tried to prove is completely false, it's just an illusion and a play on how the numbers are presented, because things happen so fast it basically generates an average all by it self, DCS application is not really loading all 4 cores, and it's not about spreading the workload either, these basic CPU Graphs give a huge false impression of the reality what is happening inside the CPU/Software, the CPU Core Utilization isn't the most practical bit of info IMO.

With multiple cores in a CPU, an application thread might not be kept on the same exact core all the time, it may switch to another core. In the CPU/Firmware/OS scheduling logic some condition was fulfilled and the thread got bounced to another core, even if there may not be some big need for that, like some other application needing room , many things come into play, yes there just might be some super under-the-hood reason in caches, a load of other reasons, which may improve performance by .. 1-2% versus just leaving it on the same core (HW thread), the CPU architecture and the performances and performance ratios between the L1-L2-L3 caches and how the CPU is structured all come into play in this and the OS has to actually be aware of this architecture to employ the most appropirate scheduling logic for that type of architecture. So even when there isn't much of other work going on that would, threads bounce, there is some kind of a "preferred core" logic, so if there's one big application thread, it usually stays on one core but it's not guaranteed, and I think I later realized there is a function in the WIN32 API i think to FORCE the application thread to a particular core (hw thread), the changes in performance would be miniscule for most CPUs IMO unless someone does a big test and finds a CPU architecture/OS combo that breaks this, other than that you migtht get less "balance loaded" graph views which is more accurate to the reality.

DCS has one main thread and an audio thread which is almost always not maxed out (i don't remember the utilization of it right now, it's like 50 if I recall).

This is a quick summary, extensive discussion was in this thread months ago: https://forums.eagle.ru/showthread.php?t=201530&page=9

That's similar how gaming performance benchmarks used FPS but have now figured stuff out and evolved to put focus also Frame Times, which I won't be explaining here ofcourse, it's a lengthy explanation.

Lp3pNYPLCD4

Example: In the middle of the video when 2 cores are enabled via affinity, two bottom cores being equal in application utilization is only an illusion or a misinterpretation more accurately, sure it's real, the actual CPU cores/HW Threads (Not HT threads), they're not equally loaded by the application, the two threads simply get bounced around those two cores to make it look like that, if you search around the thread and look at the WPA pictures you'll see the main thread being maxed(or nearly) while the audio thread much less. The taskmanager usefulness in such cases is rather detrimental, you'd be better of not having such information, would be less confusing, this is the danger of making things easier, lack of context.

Also note that sometimes I used to call a physical CPU Core a HW Thread, as traditionally there's only one HW Thread on a CPU Core, probably shouldn't, but a HT Thread is ofcourse another thing so don't mix it with "HW Thread", not interchangible, while a HT Thread is a HW Thread but not vice versa, kinda like a square/rectangle and bridge/viaduct relationships, even worse sometimes I use capital letters sometimes not when talking about application threads, i just can't make up my mind with it unfortunately. The testing from that thread was mostly without HT unless specified, so the 4 HW Threads you see are all physical cores without HT. Who the heck knows if HT threads are an actually hardware thing at all or it's all in the "mind" of the CPU/Chipset Firmware, it goes down deep so maybe only the key Intel/AMD engineers know for sure, I don't really trust the PR around this, by the time it gets to the marketing who knows how much accuracy and context the original info lost, plus it's ofcourse trade secrets, even if they're honest they would leave stuff out on purpose so full picture wouldn't be known, unless I do more research on it.

This is one of those things I wanted to go forward on and do something about it, what would be the more reliable way of looking at "CPU Utilization", but due to my business I was unable, but I might get back to it in the future. Well it's pretty much there, just looking at the CPU Total utilization, without broken down by Cores is a pretty good start. It's been a few months so I forgot a bit what exactly I was trying to get to more than that.

Also it's a bit weird why would copy protection DLLs take that much CPU over in that screenshot, you should keep watching if it's just the coincidence or it's something constant.

I use process lasso to force DCS onto physical cores only. I’ve noticed it doesn’t change FPS whether on or off, but I get significantly more stuttering when I allow DCS to use logical cores (HT on)

Yeah, I think then the idea of HT thread being invisible (for sure?) to the host OS and application is a negative in the long run, for these types of , the applications and/or the OS should then recognize these and do scheduling/utilization differently without having the user to turn HT completely off in BIOS.

Thanks for information that I already know. You didn't understand what I exactly wrote. If you know math, you can just realise that 25% from 6-core processor is 1.5, not 4. So 2 cores are enough for DCS. I've never said that DCS can use 4 threads/cores at 100% or really need it, but I've said that it uses more then 2 threads (even if I didn't count other DDLs from my sound and graphics cards) and it's true - I didn't write anything about CPU time. Also, you have forgotten about other programms in background like an antivirus, Oculus runtime, MSI afterburner, browser, etc. So 2-core processors are too weak now, even i3 has 4 cores. Because of that, I've written that 4 cores CPU is a good choice for DCS.

And how you could realise, I didn't use Windows Task Manager, it's uninformative, it even doesn't get you an infromation where is a bottleneck. But on my screenshot you can easily see it - main thread of DCS(100/6=16.6%).

The video which shows a lot benefit from 2 cores is incorrect or misunderstanding. You get up to 80% fps not only because of sound thread of DCS(only 0.45%), but mostly because of graphics threads of driver(almost 7+3+...~11% of CPU time, depends of graphics settings).

For clearly understand this, you can check "one-thread" application, for example, Stalker. It also gets a lot benefit from the second core.

In VR I use Oculus debug tool to understand perfomance which shows frametime line, so I think you don't need explain to me what it is.

X-plane 11 going to Vulkan this year(it uses OpenGl now) and will be use up to 4 cores. Also even now it can uses at least all 6 cores at 100% during loading(autogen).

I think then the idea of HT thread being invisible (for sure?) to the host OS and application is a negative in the long run, for these types of , the applications and/or the OS should then recognize these and do scheduling/utilization differently without having the user to turn HT completely off in BIOS.

HT’s are not invisible to the OS. the opposite in fact. the OS has a very detailed, very clear understanding of what they are and how to use them.

also, don’t forget that intel designed these cpu’s to compute large recurring workloads. and many of the ‘features’ mentioned here are focused on that type of work, not gaming.

for gaming, your best option is 2-4 cores with the highest clock speed you can get ($$ or overclocking, or even better - both).

Thanks for information that I already know. You didn't understand what I exactly wrote. If you know math, you can just realise that 25% from 6-core processor is 1.5, not 4. So 2 cores are enough for DCS. I've never said that DCS can use 4 threads/cores at 100% or really need it, but I've said that it uses more then 2 threads (even if I didn't count other DDLs from my sound and graphics cards) and it's true - I didn't write anything about CPU time. Also, you have forgotten about other programms in background like an antivirus, Oculus runtime, MSI afterburner, browser, etc. So 2-core processors are too weak now, even i3 has 4 cores. Because of that, I've written that 4 cores CPU is a good choice for DCS.

 

And how you could realise, I didn't use Windows Task Manager, it's uninformative, it even doesn't get you an infromation where is a bottleneck. But on my screenshot you can easily see it - main thread of DCS(100/6=16.6%).

Sure, but those are small things I consider negible, I don't run MSI Afterburner or anything in the background so it wasn't a focus point for me, but ofcourse, I just didn't mention it because it wasn't meant to be a full explanation post

Yeah I didn't include to mention "the math" cause I didn't want to repeat all thr details what I already wrote about in that thread.

Secondly I many times write things in general but use the quote as a helper for a point or two, not everything I wrote was aimed as a reply to your specific case.

I'm talking about my own case where I have 4 cores, there's little difference except the % math in the total CPU utilization, it's again a "insert specific case number", which I didn't feel was that important to do as again I'm talking in general half the time. I would have done it if I wasn't busy these days.

I wasn't giving CPU purchasing advice, I thought it was pretty obvious (after all in that thread) that if you have a quad core you'll be a bit better off than dual-core, I was focusing on whether DCS is dual or more threaded, those extra little threads aren't significant so I just ignore them, plus not sure if those run async maybe they have to wait for stuff in the main. Unless more significant components are split and actually run async, like 10-20% speed up then we could start saying more about that, and mainly if they affect FPS, that's what mostly was my test, if it affects FPS (up in the right corner in the video), that said, a large part is still going to be single threaded for the forseeable future, and the use of this "multithreaded" moniker is so ridicolous for so many reasons.

Sorry, it doesn't use more than 2 threads, DCS is still a "dual-core" application. - Yes a key distinction is to say threads not cores. Because those two threads are bouncing around on many cores

Not anymore, I have tested this out using process lasso and moved everything heavy to other threads and put DCS on two main cores, it did run but the cores were working very very hard and I was doing nothing in sim just flying around in a circle. She was running like a dog, it's much better on at least three cores now. I also had problems recording with Action and turned HT back on to fix it, without it, crashed DCS. Smooth as butter with HT?

As long as I can max out my GPU with max settings I'm happy.:)

Not anymore, I have tested this out using process lasso and moved everything heavy to other threads and put DCS on two main cores, it did run but the cores were working very very hard and I was doing nothing in sim just flying around in a circle. She was running like a dog, it's much better on at least three cores now. I also had problems recording with Action and turned HT back on to fix it, without it, crashed DCS. Smooth as butter with HT?

 

As long as I can max out my GPU with max settings I'm happy.:)

 

Well that's a bug, you should report that crash, send/upload crash log.

Yeah I was speaking at the time I tested, which is quite some time back now, I would find it bizzare for such a huge change to go undocumented in the patch notes. I would need a lot more details on how you created this test, with actual screenshots of process lasso and probably WPA even.

You mentioned recording, are you sure you didn't record when you took those numbers and this screenshot?

Out of curiosity for something unrelated, would you post a screenshot or log of your DXDIAG info (with private info removed ofcourse, if you care). I'd like to check something about the RAM/memory. Also Resource Monitor memory tab. Is that MSI Afterburner overlay?

I'd go by what the actual developers say and that has been reposted multiple times.

If I understood that correctly, there are already more than those 2 threads.

I have pretty frequent spikes in the 60's% usage and sometimes it even goes into the 80's% for a short time.

The future is more cores

The future is more cores

definitely. but it only works when the software is designed to leverage it.

and we are still waiting for games/sims that can utilize 4 cores.

it’s not easy.

try running a dogfight over downtown Nellis, and whatch that CPU usage. benchmarking grass and trees is not a challenge. ;)

Just to add my 2 cents to this conversation.

I was unsatisfied with the performance of my system on Blue Flag in VR, so I managed to push my 4790K up to 4.8GHZ which did improve things somewhat. But I was still getting long stutters occasionally and low CPU and GPU utilisation. So I decided to turn HT off, this system is only used for DCS/Sims so I don’t care if it impacts other programs. The results were higher CPU and GPU utilisation, I’m now getting around 70% GPU usage on Blue Flag, up from around 50%. And higher CPU utilisation generally as well. The results of this are generally higher and more consistent FPS but the biggest change was the lack of long stutters. I played for several hours on BF Cauc with HT off over this last weekend and even spawning on the ramp at Tbilisi in the F-18, surrounded by other Hornets, Harriers and F-15s things were very playable, which is a big improvement from before.

I’d definitely say it’s worth a go trying HT off, it’s clearly going to depend on your system and also depend on what’s causing your performance issues. But it’s certainly helped me!:thumbup:

If the GPU only goes as far as 70% then you have a bottleneck somewhere else in the system. Most likely the cpu and /or RAM amount (if it's less than 32gb that could be a factor for your stuttering ). Changing threads in your case cannot be used to determine the games limitations if the primary limitation is your system.

If the GPU only goes as far as 70% then you have a bottleneck somewhere else in the system. Most likely the cpu and /or RAM amount (if it's less than 32gb that could be a factor for your stuttering ). Changing threads in your case cannot be used to determine the games limitations if the primary limitation is your system.

indeed, 70% GPU usage in 2d mode ( not VR ) is a clear sign of a huge bottleneck somewhere.

Your CPU at 4.8G should not cause this actually, wonder what it is ?

Hyperthreading has never caused me any issues in DCS, but for those of you who say you saw an improvement without it, instead of disabling the feature entirely Bitmaster is on point with Process Lasso. Pretty easy to set up any .exe file to utilize only the phsyical cores rather than logical ones and you get you keep your logical cores to help with managing anything running in the background/multi-tasking or if you for some reason start using applications that do make more use of multi-threaded processors. Without hyperthreading your older i7's might as well be i5's. For the latest iteration, a 9900k without hyperthreading is pretty much a 9700k.

Gaming may not benefit from it yet, but overall system performance should be better with HT enabled. I have been using Process Lasso due to seeing Bitmaster mention it many times in these forums and gives you the benefits of both worlds. I recommend trying that before disabling the feature that made your processor more expensive than its i5 sibling.

Should I find myself not gpu limited @45fps in DCS VR with a GPU upgrade I'd just increase my pixel density, but for the VR user not getting 100% gpu utilization, i'd be looking into system drivers or perhaps even a DRAM bottleneck. Via supersampling or DSR for pancake mode, or Pixel Density increases in VR, you should one way or the other be able to pin that GPU til it slows to a crawl, your CPU hardly breaking a sweat and thus find the performance limitations of said gpu.

Turned HT off in the BIOS years ago already and never looked back, since having it on made the sim stutter more.

Does Hyperthreading reduce DCS performance?

if you look at the benchmarks for performance increases with HT they are minimal. even the intel claims are small and that’s with highly optimized unrealistic workloads.

you don’t run those workloads on your home PC. nobody does.

HT provides a small gain, in a small number on workloads in a small number of scenarios.