Regarding XP11, a personal comment...

[Sesquashtoo 2,846]

9 minutes ago, N1G said:

That's OK Mitch. The community is with you, so please don't take this out on yourself! We all have made mistakes. 

LOL!  

Mitch'er

[brucets 94]

59 minutes ago, Sesquashtoo said:

Gawd...am I now kicking myself. I had great XP performance in my system all along...but had a wrong CPU configuration.  Dang...all those years since 2009, and scratching my head, only thinking that H.T. was 'better' than running just your physical cores.

Ooops!  I mistakenly thought I was in the FSX page! Disregard!!

Edited April 27, 2017 by brucets
Wrong sim!!!!

[JLSeagull 191]

2 hours ago, brucets said:

Ooops!  I mistakenly thought I was in the FSX page! Disregard!!

Ooops! I mistakenly thought that I was on the 'other' page! Disregard!!

[carrotroot 77]

On 4/26/2017 at 3:19 PM, N1G said:

Yea, I did reboot etc., so it's the old "your performance may vary". Where have I heard that before?

Especially when you are comparing a 1st Gen i7 to a 6th Generation part. Nice to see that X-Plane may benefit from having HT on with newer processors.

[N1G 88]

1 hour ago, carrotroot said:

Especially when you are comparing a 1st Gen i7 to a 6th Generation part. Nice to see that X-Plane may benefit from having HT on with newer processors.

Yes, for sure!

[SteveW 1,792]

With HT enabled XP11 will put double the threads onto each core rather than one just like P3D does and it's the same for much other software too, and as such this scuppers the main thread performance of sims. It's not a better CPU to turn off HT, with P3D and FSX an Affinity mask is used to prevent that. Maybe you guys should look into steering XP11 to avoid ganging up threads onto HT cores so you can still gain the benefit of HT. Turning off HT may be a quick fix for the problem, but it's no way the best solution for any software on an HT platform. Just like with P3D and FSX there's no HT disabled configuration that can beat a properly set up HT enabled configuration

[virtualstuff 752]

Agree here Steve no way I will turn HT off on my I7 lol for several reasons ;-)

[SteveW 1,792]

If we can see an improvement with an app by turning off HT this simply proves that there's a problem with the app (and maybe other software) running in HT mode and needs something done to help it distribute across the CPU. It's a fact that some find hard to swallow, but the Intel guides do describe the issue thoroughly enough for the devs.

[Paraffin 2,197]

18 minutes ago, SteveW said:

If we can see an improvement with an app by turning off HT this simply proves that there's a problem with the app (and maybe other software) running in HT mode and needs something done to help it distribute across the CPU. It's a fact that some find hard to swallow, but the Intel guides do describe the issue thoroughly enough for the devs.

A question from a non-coder: Is it possible that X-Plane's inefficiency in distributing threads is related to the fact that it's a cross-platform app (Windows, Mac, Linux)? Primary development on a Mac, but I don't know if that's relevant.

Also, I think I remember reading somewhere that Laminar has now managed to port the full XP11 flight model to the mobile app version that runs on smartphones. Again, I'm not a coder, but that might suggest some difficulty in optimizing the code, compared to something like a Windows-specific flight sim.

[SteveW 1,792]

Yes that's a good point. However apps on Windows need not code specifically for if HT is enabled or not since it's a Windows Operating System job to deal with the concerns. Even so that doesn't happen too well for some apps and so they need help with steering such as with P3D/FSX using an Affinity Mask. XPlane will be coded in a very similar manner, a main process will run the UI and Visual rendering, supported by a threadpooling process managing a number of threads doing the background work. because the main process becomes intense with rendering its performance would be reduced if the process is on an HT core being shared with another of those processes. Since XPlane is cross platform app it might preclude specifically coding for HT, but that's not entirely necessary for Windows apps like those anyway, a 3rd party tool would be used to improve things if the Windows version of the app doesn't include for specifying core affinity.

[SteveW 1,792]

...Further, a reason why FSX and P3D don't suffer from such a performance decrease with HT and no Affinity mask specified is because the second process is the least active and so with no AM specified it shares the first core with the main process each on one logical processor of that core, and so does not cause such a degradation in performance as it might if the second process was more intense. Even so we still use only one process per core, not per logical processer, for those

[Cruachan 705]

Hi,

I'm with Mitch on this one. However, I do have to say that, while very pleasing, I'm a little surprised at his success with a 4-cored cpu. I've been assuming that my 8-cored (physical) cpu with HT=OFF and Threaded optimisation=ON is the sweet spot for X-Plane 11. Threaded optimisation=OFF reveals a microstutter fest with a drop in frame rate which threatened XP's usability, whereas ON is flight sim heaven 😀

Steve knows all too well the trials and tribulations experienced by me while experimenting with HT=ON/OFF with P3D. In the end the results spoke for themselves with OFF being the best setting, albeit with a maverick affinity mask setting of 21760 which, for whatever reason, randomises the core selected to handle the main thread each time the sim is run. 

Really, all this does is underline system specificity and the importance of being prepared to spend time experimenting to find settings that best suit your hardware/flight sim combination. Happily, to date I have discovered no downsides to turning off CPU Hyperthreading (other than slightly reducing some formal benchmarking scores) as everything else seems to be running very well (my rig is not used exclusively for flight simulation). Also, as another poster mentioned, the CPU runs cooler (never higher than 50C) which supports a stable overclock and helps to preserve longevity. So, in other words, if you have the overhead then it might be worth trying the effects of turning off CPU Hyperthreading. You never know, like Mitch, you might be surprised at the results.

Flight Simulation has proven itself to be a unique software environment which frequently requires unique solutions to achieve optimum results.

Regards,

Mike

 

[SteveW 1,792]

Hi Mike,

I would always recommend coming down the heat curve a little so that HT operation can be accommodated within the thermal scale of overclocking, rather than push the ultimate overclock like I might to play Doom or something like that. Since these sims use a lot of system resources other than GPU. After doing some testing this week on Hyperthreading I'm sure I can get more out of your rig with it enabled, XPlane or P3D. The thing is with eight core CPUs its easy as falling off a log, they are like four core CPUs with HT enabled on steroids, and no drawbacks with unwanted core sharing, so they work great with HT off too. I would still insist that ultimately I can get more out of your rig with HT enabled, it is after all only a mathematical exercise, 16 LPs would be positively delicious.

[SteveW 1,792]

...heat...it is spoken about as if it's a problem that can somehow be remedied by turning off HT. What's actually happening is that it's actually doing less work with no HT; work=heat. So that reduction in heat means the overclock can go higher for single thread speed. As Mike says in any system there's a lot of stuff other than that to consider. With HT on it'll do more work across the CPU, with HT off we can overclock it more for single thread performance. Some motherboards can accommodate a single core overclocked, a neat setup might target that overclocked core with the main process of the sim and the CPU more able to distribute the heat.

 

Obviously I'm describing fairly advanced techniques, not for everyone. Turning off HT saves a lot of head scratching and it's not a big deal in performance with these sims ultimately, but good to know it's there and we can get more out of it if happy to try some techniques.

[Cruachan 705]

1 hour ago, SteveW said:

 I would still insist that ultimately I can get more out of your rig with HT enabled, it is after all only a mathematical exercise, 16 LPs would be positively delicious.

Hi Steve,

It's perhaps a shame we don't live closer to each other as I would have liked to have been able to show you how the rig is performing. Still, it's always nice to know that there is still something in reserve should I need more and wish to experiment further. Meantime I'm very content with what I have .

....and, I'm expecting it's about to get a little better - keep an eye on my signature

Regards,

Mike