One more informative link I had overlooked including in my latter post above:

 

http://www.avsim.com/topic/477057-a-frame-time-analysis-of-p3d-v3-effects-of-cpu-affinity-frame-lock-and-ht/

 

Happy reading (...and flying !) B)

 

GaryGB

And don't go into the task manager Set Affinity menu item and press OK as it can reorganise the layout.

I was under the impression that you would only mess up the threading if you enabled or disabled a core via that method.

 

So you mean to say even just going to affinity and then pressing ok will disturb the threading?

 

For some reason if I don't do that then one of my lps will always be underutilized no matter what AM I set in the config.

 

Regards,

Shanan

It's not underutilised. But if you mess with the affinity after the sim started, you'll get multiple jobs on one LP, making you think that it's better utilised. It's not, it's unnecessarily over-utilised.
 

The fps is disconnected from the performance of the background jobs of the sim. The background jobs take any number of seconds. Watching the fps is not particularly important because we can make it increase or decrease markedly by adjusting sliders, screen size, or CPU GHz.

We can make the fps change markedly by delaying the background tasks. We can make the fps spring up a few. Seeing this behaviour on the shift-z display fools us into thinking the sim is running better. It's not, it's running with an inconsistent framerate.

Counter-intuitively, when the sim is performing better, we get a slight reduction in fps, one or two fps, and gain a better overall sim performance.


Take a look at four jobs vs five jobs. Five jobs shows a few fps more but a lot more delta:

1360=4 jobs HT enabled, 1364=5 jobs HT enabled, 60=4 jobs HT disabled, and 62=5 jobs HT disabled.

Where five jobs shows a few fps more, but a larger delta, is because when the background is delayed, the fps runs free. Taking a high performance reading shows sawtoothing of the main rendering with five jobs.

With four jobs you'll see the first run at 80% or more, the second maybe only 30%, the other two around 40 - 60%. But max out the sim and they all get going, don't worry.

In a nutshell, a fifth job slows the sim down and introduces instability. And HT enabled is better than HT disabled. Maybe with a 5GHz CPU and Mega GPU we might see a fifth core utilised. But at the moment we only need four LPs unmasked for the sim.

Ok so currently I use an AM 248 (00,01,11,11) HT ON.

 

I have scenery sliders all at the right and I see lps 5-8 all maxed out when around a dense scenery area such as Flytampa LOWW. But lp 4 is only at 30% use even thought the sim is maxed out?

 

The main thread (lp 3) is of course maxed out as well.

 

Am I going to see smoother performance if I assign 4 lps instead of 5 in this case?

 

I have a Skylake 6700k at 4.7ghz. Which is why I was wondering if it could be beneficial to use 5 jobs over 4 jobs.

248=(11,11,10,00) unmasks five LPs, and spares core zero, thus utilises three cores. The first sim job gets a core to itself, the others share cores to a disadvantage. Instead, if you have four cores and want to reserve core zero, use 116=(01,11,01,00).

 

Take a look at the three core performance of 116 vs the four core performance of 85. 85 only just outperforms it:

 

 

Five cores on 341 is worse, since it's 5 jobs.

 

The differences in the first minute or so, are due to the way the concurrent processes play out. Pay more attention to the situation at the two minute mark.

 

The reason 116 performs well is because when job three maxes out, job two is dormant. Bunching these two on a core comes with the least disadvantage. Combining any other two results in contention for core throughput all the time.

 

You got to remember that with HT enabled, even though we get double the number of processors, they are two LPs to a core. Two elephants at the same water hole consume the water twice as fast. The difference with HT enabled is that switching time across the entire CPU is overall reduced by more or less half, amounts to quite a bit of go.

Ahh thanks for that. So in conclusion it would be better to have the two scenery loading jobs on separate cores? Even though I have my clocks at 4.7ghz? I assumed that with that speed the cores jobs would have enough headroom to work on a single core without competing for throughput.

 

Also with 116 that would mean I have one less job devoted to scenery loading, wouldn't that affect performance? Because even with 5 jobs the 3 jobs doing scenery loading are maxed out. I imagine I will have scenery loading issues if I reduced that to 2?

 

Ultimately I don't want to have to lower scenery settings to compensate.

 

Thanks for all the help so far. This has really peaked my curiosity when it comes to performance.

Did you not see the graph? Five doesn't work. That was with P3D v3, PMDG 737 and Mega Airport EHAM.

 

In the graphs the difference between three and four cores was small, four being better. I'm talking cores not LPs. You can assign another LP to another job, but the job is discarded. But on a four core you've no more cores to assign, so you can only rob the throughput of a core already occupied. Seems fairly straightforward, but then look at the five real cores, less performance than four, or three.

Forgive me if I seem like I'm being ignorant.

 

But I thought you said in a earlier post in another thread that with higher clock speeds and scenery settings the sim may begin to make better use of 5 LPs.

I did, but I've had no reports from anyone that they have been able to get that. Chances are we won't. And anyway, you were talking about another job that could only occupy the second LP of a core, sharing that core, since you have only four cores. Not quite the same thing. HT On doesn't net you any more cores, just switching performance.

So, what's the verdict?  8 cores helps P3D performance?

I see. Thanks again. I guess I will revert to an AM of 116 in that case.

 

One more thing, should I lasso all other addons and processes to run on cores other than the main thread only or is it better to make them run on cores not used by the sim at all?

So, what's the verdict?  8 cores helps P3D performance?

From what I gather, yes and no. The other cores simply give you more headroom to run other addons and processes/programs and dedicate 4 cores to the sim only. Whereas with a 4 core you have to squeeze the rest into 1 core and dedicate 3 to the sim or use 4 cores for the sim but run other addons concurrently.

 

Helpful if you have many other addons running at the same time.

 

Correct me if I'm wrong Steve.

 

Regards

Shanan

Use the batch methods or specially written apps to start addon apps with affinity that run when the sim runs. Lassoing apps can stop them working correctly. Avoid lassoing apps that control their own affinity like P3D.

Use the batch methods or specially written apps to start addon apps with affinity that run when the sim runs. Lassoing apps can stop them working correctly. Avoid lassoing apps that control their own affinity like P3D.

 

Ok. But my question is, do I just need to move them off only the core that the main job of P3D runs or all other cores used by P3D as well?

 

For example with an AM of 116 (01,11,01,00), should I just move them off LP3 into any other LP, or move them all to LP1 and LP2 which are totally not used by the sim?

Yes, keep them off of core 1 altogether LPs 2 and 3, and let them run on core zero, LPs 0 and 1. You can also let them utilise LP7 with LPs 0 and 1.

Thanks. Would it make a significant difference if I moved all other applications to those LPs too (chrome, anti-virus, plus all other apps running in the background)?