Prepar3d: settings and news

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TSR2
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Re: Prepar3d: settings and news

Post by TSR2 »

Its a strange one, The MS article he references relates to how SQL2000 handles processor allocation. Remember SQL 2000 was in the days before x64 or multi core cpus.

I've just checked the default processor affinity on my system for P3D without any tweaking and, by default, it uses all cores :dunno:
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Re: Prepar3d: settings and news

Post by speedbird591 »

TSR2 wrote:I've just checked the default processor affinity on my system for P3D without any tweaking and, by default, it uses all cores :dunno:
Did you read his second post in the second link that I gave you? He says that P3D is optimised to use every other core (i.e. one thread of two on each core) as using every core is inefficient so what they are trying to achieve is no threads on core one, reserving it for the OS, and one thread each on cores two, three and four. That's what they're trying to achieve. If you read it through it might make more sense to you.

Read the threads, Ben or I'll throw things at you and never tell you anything else again. I'm trying to do some work here :lol:

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Re: Prepar3d: settings and news

Post by TSR2 »

But the OS, certainly later OS's do this for you. That's why I'm struggling to get my head around it :lol:
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Re: Prepar3d: settings and news

Post by speedbird591 »

There is no way I could ever begin to get my head around any of it :lol:

I just do what I'm told and if it doesn't work I put it back. I don't understand any of it :lol:

And that includes binary. Anyway, that was fun - I'll see what else I can find to wind you up :lol:

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Re: Prepar3d: settings and news

Post by TSR2 »

Here we go, one of these has no affinity mask defined, one has AF=84 and one has AF=14

All in P3D, loaded with the default time tonight, then changed to "day" in the time and season settings. All take as near as possible to the same area / speed / alt. You tell me which ones which? By the way I only have a quad core. Its also worth mentioning that depending on which post you read on which forum, FSX / P3D can only use physical cores so the hyper threaded ones don't count (I don't have any HT ones :lol: )
;)
No.1
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No.2
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No.3
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Re: Prepar3d: settings and news

Post by speedbird591 »

Well, I know which is which because you've already said that it's best without an affinity mask :lol: At least you know you've got nothing to gain by adding one! Result! :lol:
Ben wrote:Its also worth mentioning that depending on which post you read on which forum, FSX / P3D can only use physical cores so the hyper threaded ones don't count (I don't have any HT ones )
I wouldn't have posted it if I thought it was idle conjecture (oh, alright, I might have done :lol: ). This was actually a thread on the official Prepar3d forum by a Lockheed Martin Prepar3d software engineer so I thought it might be of interest :( I think he was breaking the news that, although it was intended for v2.0, it's already active now but nobody knew. He says here that P3D will select alternate hyperthreaded cores by default but he recommends using the affinity mask to reserve core one for the OS.
Zach Heylmun, Prepar3d Software Engineer wrote:Prepar3d 2.0 is targeted at improving performance. We are working to take better advantage of multi-core processors by threading off more of the computation to background threads. That being said, prepar3d 1.3 is actually able to use hyperthreading today. By default, Prepar3d will usually only use every other core on a hyperthreaded processor ( i.e. one thread per physical core ). This is the desired behavior because most of the tasks offloaded to background threads are related to I/O, and hyperthreading does not perform well when both threads are waiting on I/O tasks.
And to prove it, here's my CPU resource manager showing hyperthreading being used in P3D with the affinity mask set to 84. (I'm back home now ;) )

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Main core 1 (CPUs 0 and 1), reserved for the OS, has one thread working and one parked. The other three main cores have one thread on each core working (in P3D) and one thread on each core idle. Which is what Zach says is the desired behaviour and what is also illustrated on his post. So, I dunno. It does work but if you haven't got hyperthreading then I guess it can't work on yours, Ben.

I bet I can guess what's top of your christmas list :lol:

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Re: Prepar3d: settings and news

Post by TSR2 »

:lol:
Maybe I should put my blistering performance down to Windows 8 :-O :hide:

There may well be some mileage in it mate, just that I'm not seeing the benefit of it, but others might :thumbsup:

And it is an interesting discussion. I remember a similar topic years ago by Phil Taylor just before he went to Intel and it produced a huge amount of discussion. I think there is another element here, and that's just how much work is being off loaded to the GPU as that's the way many of the modern systems are designed, and what about intel systems that do GPU processing on the CPU etc. Way too many variables for me to compute :agree: :lol:
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Re: Prepar3d: settings and news

Post by TSR2 »

I'm intrigued by this so I did another experiment.

This time in FSX, with no affinity mask, core 0 is running full tilt, while 1.2.3 are idling between 10 - 25%. When I apply an AF of 14, core 0 is sitting between 30 - 40% core 1 is full chat and 2,3 are between 20- 30 %.

So there is something in it, for me, I'm only seeing an improvement in FSX, and even then its still only using all the capacity on 1 core (probably due to the way FSX is written) but in P3D, no AF mask gets me all 4 cores doing the needful, I wonder if this alone explains why P3D is "smoother" than FSX :dunno:
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Re: Prepar3d: settings and news

Post by speedbird591 »

Re the problem in P3D with VFR traffic not showing. This has apparently been accepted by LM. So hopefully it'll be on the list of things to do for v2.0.

There's a discussion on Avsim about 'Out Of Memory' error messages/crashes in P3D. It's happened to a few people who are trying to to run extreme scenery with a lower spec machine and isn't specific to P3D of course. It happened to me regularly in FSX on my old laptop but not with the new. What's interesting with respect to P3D is the question of whether the 'problem' is exacerbated by the lack of a startup/setup screen. Currently you may have to reset the sim four or five times to set up a situation adding to memory usage before you even begin flying. The conversation gets increasingly technical and I don't understand most of it but it's here if you want to read it:

http://forum.avsim.net/topic/384873-out-of-memory/

Interestingly, someone's posted a link to a Microsoft FixIt for OOM crashes. There's an explanation of the cause, an auto fix, or instructions for a manual reg edit here. I've done it even though I haven't had a problem so I assume that it's now less likely to happen than before :lol:

http://support.microsoft.com/kb/947246

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Re: Prepar3d: settings and news

Post by TSR2 »

Cheers Ian. You can certainly see that P3D uses a lot more memory than FSX when you look in task manager. I wonder if its because it uses all the CPU cores better though. I.e. If you're hammering 4 CPU cores instead of 1, the pre caching of that data in RAM will use more of it so as it can keep feeding the CPU. I've not had out of memory errors myself, but it could certainly account for it.
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