7800x3d CPU usage

[X_legio]

Hi there,

 

finished my new rig with the 7800x3d  Cpu, with afterburner I noticed that the cpu usage is max 75% is it normal ?

Ram is 32gb and GPU 3080TI Reverb G2

Edited February 25, 2024 by X_legio

[X_legio]

No ideas ?

[Hiob]

21 hours ago, X_legio said:

Hi there,

 

finished my new rig with the 7800x3d  Cpu, with afterburner I noticed that the cpu usage is max 75% is it normal ?

Ram is 32gb and GPU 3080TI Reverb G2

 

Yes, because DCS doesn’t use all eight cores. Even 75% is already pretty good, suggesting that probably six cores operate full bore.

Try to configure Afterburner to see the load of every core and it gets clearer.

[X_legio]

37 minuti fa, Hiob ha scritto:

Yes, because DCS doesn’t use all eight cores. Even 75% is already pretty good, suggesting that probably six cores operate full bore.

Try to configure Afterburner to see the load of every core and it gets clearer.

Ty sir, will do it 

[skins45]

Also worth noting that you're probably GPU bottlenecked with the 7800x3d.  I've found that it's a pretty even match for the 4090 so anything "less" (no insult intended) will not use the 7800x3d to the max.  But as others have said, since multithreading isn't "all-threading", you might even be running 7800x3d to it's maximum utilization that DCS can use.

[edmuss]

I typically see about 75% with the 7800x3D and 3080ti as well, I shouldn't worry about it

[kksnowbear]

I have to agree with the others here.  I also have a 7800X3D and have built several over the part year or so (paired with 3090, 3090Ti, or 4090, although not using VR).

One of the biggest frustrations for me personally is to have a very capable CPU and see how much of it's ability is *not* being used.  It really is a shame that you could benefit from that extra horsepower, and it's sitting there idle.

BTW this isn't just DCS in my observation.  Other sims do it too - and in my experience, at least one of those is far worse at times.  I haven't studied it in detail, but casually and anecdotally, I might even venture that DCS is among the *better* one at using the CPU.  A valid conclusion would require a lot of time and effort I just don't have.

Anyhow, best of luck

Edited March 1, 2024 by kksnowbear

[Hiob]

I think some of you are not totally aware of what is going on here. 

You are probably aware by now that the shown cpu usage is due to the number of cores used.

However, not all software is equal in regards to how well it can be parallelized for computing. Some applications like rendering (cinebench e.g.) profit enormously from more cores, for others, like games, there comes a point of diminishing returns pretty soon. This parallelization (is this a word?) needs an overhead that deals the tasks and collect and synchronize the results if necessary.

I‘m not saying, that six cores is the ultimate limit - that will depend on the game, but a lot of games only use something between 2-6 cores. Some use more, but the point I‘m aiming for is, that this kind of metric will almost never show 100% on a 8+ core cpu and that shouldn’t worry you. What makes the x3d a great cpu is its cache, not the core count.

[kksnowbear]

Not sure who you're referring to as being 'not totally aware' - but I can assure you I understand multicore CPUs enough to know they are typically being underutilized.  In some cases, problematically so.  (Not to get too far off here, but I can show you one example in a sim which very clearly shows a CPU being so poorly utilized that it actually causes a high-end GPU to run like a 1080.  And yes, I proved it, and duplicated it reliably.)

I also understand what makes these X3D CPUs great - already built several running DCS and many of the predecessors (5800X3D) as well.  And I've already gone on to show that even these wonderful X3D units (both AM4 and AM5) are subject to the same problem outlined above.

I'm just saying it's still underutilized - and it is.  The reasons why - particularly that it might be hard on the developers (not my problem TBH) - don't matter. 

For example: It's easy to see my GPU is working his tail off, being close to 100% utilized sometimes.  That's what I paid for.

But then I see cores/threads on the CPU sitting at (much) less than 50% usage - often less than 25%....sorry, but that's just performance left on the table.

In fact, although TBH I cannot claim to know for sure, the evidence supports the conclusion that the problem I describe above would be substantially mitigated, *if* the software were utilizing the CPU effectively.  (Again, to be clear: This is NOT in DCS - but it's still a real-world example, in a well-known flight sim)

No one's questioning what's more difficult to attain or program, or which applications do it better or worse.  Those are details for the software people to work out, not the end user.

It's not accurate to imply a CPU can't be 100% utilized (or at least much , much closer than they sometimes are).  Again, the issue is the software isn't effectively utilizing what's there.

Edited March 1, 2024 by kksnowbear

[Hiob]

Well, when the GPU is already maxed out, what do you expect as a profit from a higher utilization of the CPU? There can only be one bottleneck at a time, and in your example, if I got it right, its the GPU.

However, I digress. I didn’t mean to be condescending - sorry if it read like this. I was just giving a more detailed explanation why seeing something like 75% utilization (or 50 or 25 for that matter) is to be expected and totally normal.

DCS seem to use a maximum of six cores currently (not 100% sure) - at least in VR. Given the MT journey just started, I find that to be satisfactory.

[kksnowbear]

No worries, I wasn't offended, just wasn't sure who you meant.  I welcome informed discussion, that's what discussion forums are for

Your point is well taken about the GPU being tied up and thus not much else for the CPU to do.   What I'm referring to (sorry it wasn't clear) is the times when I see the GPU usage drop badly, because the CPU usage is even lower still.  Doesn't happen often, necessarily, but it's a real thing I've seen first hand, and can duplicate at will.  It first came up when a customer who I had just finished a build for, called me and said, hey, why's my shiny new 3090 dropping from 120 to 45 FPS at times???  Something's wrong!!

Looking into it, I discovered that the CPU was only being used maybe 50% in total across all it's cores (a 5600X with a 3090 at the time).  Bad.  Really bad.  The sim was obviously very busy, but the CPU is so underused that the GPU becomes bored, only being utilized itself ~50% at that moment.  There's nothing wrong with the CPU or GPU (tested same on completely different hardware).

Later on, he changed to a 5800X3D, which helped but the problem was still there.  I was also using a 5800X3D at that time, and saw the same effect on my own machine - which is when I tested it with a 1080 and got roughly the same frame rate as a 3090 in that situation (just the GPU was now much more utilized, for obvious reasons).  That's bad.  The CPU is being so badly underutilized, it can only load a 3090 to the same level as a 1080 can do.

Since that time, I have moved to a 7800X3D, and I'm also doing a 7800X3D build currently for another DCS player.  And, no big surprise:  The 7800X3D does increase frame rates on the same GPU, since it's able to keep them busi(er).  But it is also still not being near fully utilized - and the GPU is still being under utilized because of it.

Basically, this means I'm/we're having to throw 200% the hardware capability at it, to get what should be attained with half as much, because it's obvious that half (at least) isn't being used as it should be.  I would respectfully not call this (in this case, specifically) normal and to be expected (my example, not yours).  Like my client said that day: Something's wrong.  If I can get the same performance (in FPS) from a 1080 as a 3090...something's really wrong.  And it ain't hardware

When it gets to the point that the GPU isn't being fully utilized because the CPU isn't being utilized (and both are still showing plenty of capacity available)...well, I consider that a big problem.

Anyhow, I don't want to get too far off course, but it is 'on topic' because the question was about CPU utilization.  The point I'm trying to illustrate is that it's fairly bad in many cases, although as I said DCS seems to be better in my casual anecdotal observations.

And I believe you're right about the "MT journey" just starting, and I'm looking forward to further progress.  I can say absolutely there's at least one sim out there that could stand to learn from DCS in that regard.

Edited March 2, 2024 by kksnowbear