Turning off hyper-threading had quite an impact on my P3Dv5

[G-RFRY 1,712]

I have HT off no AM P3D runs on all cores temps lower.

HT turned off in the BIOS ASUS Formula MB.

Edited April 19, 2020 by G-RFRY

[Jeff_Fortuna 59]

I thought it would be interesting to add a dissenting data point here. On my system - 9900k with a 2080 ti and very high settings at 4k, turning off HT is a total disaster. It causes long stutters of up to a couple of seconds as core 0 is overloaded. With HT on, the load is spread quite evenly over all 8 physical cores with good usage of hyperthreading. This is exactly what I would expect. Regardless of what threading library is used, HT should be handled intelligently. It may not work well in all situations - and on all systems - however, on average it shouldn't cause major problems. Therefore I would suspect that if, on a 9900k, P3D runs much better with HT off, something is wrong somewhere. I'm not denying that HT off may work better for some, but if one has a 9900k, I would encourage these folks to push the system harder and then try to figure out why the system doesn't run better with HT on. In other words, try to take advantage of what HT offers. 

[Sethos 4,343]

3 minutes ago, Jeff_Fortuna said:

I thought it would be interesting to add a dissenting data point here. On my system - 9900k with a 2080 ti and very high settings at 4k, turning off HT is a total disaster. It causes long stutters of up to a couple of seconds as core 0 is overloaded. With HT on, the load is spread quite evenly over all 8 physical cores with good usage of hyperthreading. 

I had exactly that if I did so by using Process Lasso to do the masking. Extreme stuttering, would basically freeze up for seconds as several of the physical cores would just be jammed at 100%. However, doing it through the .cfg with the exact same masking was a completely different beast. Outside of that, the performance with HT on was also perfectly fine in most areas. However, the major difference came when trying out OrbX's SoCal, taking off out of KLAX.

Edited April 19, 2020 by Sethos

[Ianrivaldosmith 5,317]

4 minutes ago, Jeff_Fortuna said:

I thought it would be interesting to add a dissenting data point here. On my system - 9900k with a 2080 ti and very high settings at 4k, turning off HT is a total disaster. It causes long stutters of up to a couple of seconds as core 0 is overloaded. With HT on, the load is spread quite evenly over all 8 physical cores with good usage of hyperthreading. This is exactly what I would expect. Regardless of what threading library is used, HT should be handled intelligently. It may not work well in all situations - and on all systems - however, on average it shouldn't cause major problems. Therefore I would suspect that if, on a 9900k, P3D runs much better with HT off, something is wrong somewhere. I'm not denying that HT off may work better for some, but if one has a 9900k, I would encourage these folks to push the system harder and then try to figure out why the system doesn't run better with HT on. In other words, try to take advantage of what HT offers. 

Im on a 9900KS. With HT on, the scenery stutters to hell. With it off, it’s super smooth. 

[Quasimodo 505]

2 hours ago, fppilot said:

I would love to gain a better understand of that.  If you have time would you PM me a bit more about it?

imagine a single core cpu. With HT on you get 2 logical cores. With affinity mask = 3 (binary 11) the threads are divided across both logical cores. With Affinity mask = 1 (binary 01) or 2 (binary 10) the load is taken up by only one of the logical cores either Core0 or Core1 and the other is left completely ideal. The one logical core that's in use gets to use the entire power of the Physical core just as if HT was off.😁

Of course this assumes that only one app is running on the system which is never the case.

Edited April 19, 2020 by Quasimodo

[Ianrivaldosmith 5,317]

@Quasimodo How do you run yours? 

[Quasimodo 505]

Just now, Ianrivaldosmith said:

@Quasimodo How do you run yours? 

HT off, No affinity mask

[Ianrivaldosmith 5,317]

I think I finally just figured mine out now. 
I run affinity mask so that only 8 cores are on (disabling HT, via the mask). 
 

then in the sim itself I set Vsync off and triple buffering off, and frame slider to unlimited. 
then in Nvidia inspector I have set p3d maximum FPS at 97 (3 less than 100hz of my screen) using g-sync. 
 

doing this has stopped core 0 being pegged at 100% all of the time and now the sim is super super smooth! And fast loading ground textures. 
 

https://ibb.co/G7DDyWD

edit:- just tested London with orbx = stutterfest! 

Edited April 19, 2020 by Ianrivaldosmith

[silentsage 19]

The reason hyperthreading can cause stutters is this:

Windows has an operating system feature called CPU parking.  When this feature is enabled, the OS will try to move threads between cores with the objective of minimizing the number of active cores in use at any time (i.e., it will try to pack the threads into the smallest number of cores running at 100%).  The unused cores and "parked". This is done to conserve battery life in laptops - the fewer the number of active cores, the less power is needed.

The problem with this from a gaming standpoint is that it takes time to move threads between cores.  While the thread is being moved, it stops executing, and hence the stutters.  Disabling hyperthreading (either in the BIOS or with an affinity mask) eliminates the problem. 

I learned this from a gaming site.  You can turn CPU parking off by doing the following:

1. Disable CPU parking
   1. Go to Regedit
   2. Find this key:-  " 0cc5b647-c1df-4637-891a-dec35c318583 "      
   3. Within this key, there is a value called:  " ValueMax "
   4. This value represents the % number of cores the system will park - the default 100%  ie:  all Cores are potentially park-able
   5. Change the value from 64 to 0 so the " ValueMin "  and  " ValueMax " are both zero
   6. You will have to find the key a few times and repeat the process for each time it is found - the number of instances will depend on the number of power profiles in your system
   7. Do a full shutdown and power-off and cold-re-start

This info is a few years old, it is possible that this method is out of date (but you can try it.

I stopped using it because it is easier to simply disable hyperthreading. 

 

[fppilot 4,371]

1 hour ago, Quasimodo said:

imagine a single core cpu. With HT on you get 2 logical cores. With affinity mask = 3 (binary 11) the threads are divided across both logical cores. With Affinity mask = 1 (binary 01) or 2 (binary 10) the load is taken up by only one of the logical cores either Core0 or Core1 and the other is left completely ideal. The one logical core that's in use gets to use the entire power of the Physical core just as if HT was off.😁

Of course this assumes that only one app is running on the system which is never the case.

I understood what HT does.  What I asked about was not about the basics of HT but how you effectively disable BIOS-set HT with AM.  I traded PM and have a better understanding.

[Quasimodo 505]

2 hours ago, fppilot said:

What I asked about was not about the basics of HT but how you effectively disable BIOS-set HT with AM

Sure and my post answered that precisely in a clear and un-bloated way. The way any question should be answered. Sorry you took offence. I won't bother next time.😁

Edited April 19, 2020 by Quasimodo

[captain420 3,099]

It's still a shame that we still need to wonder about these kinda settings in P3D v5? This all reminds me of FSX all over again. Seriously we have to mess with endless settings in different combinations to get our sim to run they way it should out of the box? If anything it should be up to LM to get this stuff sorted out so that us simmers can actually use our precious time to enjoy the sim instead of tinkering. This is one thing that really frustrates me about FSX/P3D. I really hope MSFS 2020 isn't going to be anything like this.

[kaha 205]

On my 9900K I switched off HT in the BIOS. As temperatures are lower with no HT I was able to overclock to 5Ghz on all cores, also in summer at ambient temperatures of 26 Celsius in my room.

Works like a charm.

 

Karl

[joby33y 152]

1 hour ago, captain420 said:

If anything it should be up to LM to get this stuff sorted out so that us simmers can actually use our precious time to enjoy the sim instead of tinkering. This is one thing that really frustrates me about FSX/P3D

Fire up your sim, with default scenery and a stock airplane.  How does it run?  If you get frustrated, then you need a faster PC.  

Now, head to your favorite complex scenery add-on area (Orbx SoCal seems to be the best example), and fly a complex aircraft around. Different level of performance.  

Bottom line :  all the tinkering in the world, or "LM sorting stuff out" will never normalize the performance between those two scenarios.  I get your frustration!  I've tinkered with HT on and off, and Lasso'd my a** off until I'm blue in the face.  I'm with you, but I am not blaming LM for the fact that we choose to add massive complexity, and therefore performance killers, to fly over beautiful sceneries, or precise simulations of Boeing or Airbus Airliners.  You make your own call every day when you fire up your sim.  If I stop and think about the amount of money I've spent over the years chasing FSX and then P3D performance with yet faster, faster PC's, its just scary.  But a lot of fun.  

[fppilot 4,371]

2 hours ago, Quasimodo said:

Sure and my post answered that precisely in a clear and un-bloated way. The way any question should be answered. Sorry you took offence. I won't bother next time.😁

Sorry you felt I was offended.  I was not.  Just appeared to me you did not understand my question.  Thats all.