Hyperthreading

[makapala]

I realise that Hyperthreading has largely been discarded by Intel in Gen 9/10 but why does it affect my 7700hq chipset Prepar3d performance so badly? With it on, I can spend hours trying to get various cpu's to play nicely.. but with them off.. it runs faster, smoother and cooler.

 

Why?

[John Dow]

Each system seems to react differently... my i7 970 would suffer badly with hyperthreading turned on, in FSX at least, my i7 4790K runs better with it enabled.

 

I don't know what affinity mask settings will do to ht settings, I've basically given up trying ti set any affinity.

 

[makapala]

I sit and watch the cpu activity in afterburner and notice that with HT off the cpu's share the P3Dv5 load evenly and without too much fuss at all. With HT on, one thread takes a MASSIVE hit and some of the threads sit entirely idle. You can tweak affinity masks but it seems to just shift the blockage somewhere else. Also, the laptop on board GTX1070 GPU memory is better utilised with HT off. It's pretty messed up.

[John Dow]

If flightsimming is the only heavy work your computer does and you don't need ht on, just go and fly I say. 

[magnetite]

There's some apps like video encoding where having HT on really shines. However, with FSX/P3D that is not the case. Seems like with HT off, the "real cores" don't have to fight for resources with the HT cores. While if it's on, the real cores, and the HT cores are fighting for resources.

 

Video encoding apps use some type of task scheduler using a thread pool, where they start and "queue up" jobs across multiple threads. Sometimes it might ask a job to wait for something before starting, etc. It's much more manageable. I don't know all the technical details since I'm not a programmer, but that is the general idea.

[Orbx Flyer]

On 7/1/2020 at 8:05 AM, John Dow said:

Each system seems to react differently... my i7 970 would suffer badly with hyperthreading turned on, in FSX at least, my i7 4790K runs better with it enabled.

 

I don't know what affinity mask settings will do to ht settings, I've basically given up trying ti set any affinity.

 

Your i7-970 is a four core...and the proper setting for your CPU will be this.   This will free up Core 0 to run BIOS, while cores 1-7 will process P3D or FSX threading.  Your P3D will run beautifully...

[JOBSCHEDULER]
AffinityMask=254

[John Dow]

6 hours ago, Orbx Flyer said:

Your i7-970 is a four core...and the proper setting for your CPU will be this.   This will free up Core 0 to run BIOS, while cores 1-7 will process P3D or FSX threading.  Your P3D will run beautifully...

[JOBSCHEDULER]
AffinityMask=254

 

All very well in theory but it never worked that way.  HT made FSX crawl no matter which affinity setting I tried.  Turning off HT and not setting any affinity allowed FSX, which is a single core application, to run the smoothest. 

[makapala]

On 7/2/2020 at 2:12 AM, John Dow said:

If flightsimming is the only heavy work your computer does and you don't need ht on, just go and fly I say. 

 

Well seeing as my profile pic features a MASSIVE telescope, maybe not.. but hey I live in Newcastle and the weather allows maybe one good astrophotography session a year lol

[Guest]

I have been doing a lot of reading about HT and decided to turn it off. Well ....it has done the trick for me in P3Dv5. Everything is working better, Massive FPS in all regions including True Earth, the sim now shuts down properly, in a word "SORTED". I am even going to try Vector again. The stuttering and tearing also seems to have all but dissappeared, I am truely amazed. If you have a Intel processor then my suggestion is to switch Hyperthreading OFF. Give it a try!