Author Topic: Question for Umberto about GPU RAM and 64bit O/S  (Read 7859 times)

altstiff

  • Jr. Member
  • **
  • Posts: 78
  • My F/O is a dog
    • Visit my flightsim blog..
Question for Umberto about GPU RAM and 64bit O/S
« on: November 04, 2012, 09:22:54 am »
I know that on a 32bit O/S the GPU's RAM is mapped through the Virtual Address Space. On a 64bit O/S is the GPU's ram mapped the same way?

The reason I ask is that since I have upgraded to a 3GB GPU I have seen more OOM errors than before (with a 2GB GPU).

Thanks in advance

virtuali

  • Administrator
  • Hero Member
  • *****
  • Posts: 41582
    • VIRTUALI Sagl
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #1 on: November 04, 2012, 11:47:00 am »
I know that on a 32bit O/S the GPU's RAM is mapped through the Virtual Address Space. On a 64bit O/S is the GPU's ram mapped the same way?

Absolutely not, that's the main advantage of using a 64 bit OS, even if running just 32 bit apps: your GPU will not "steal" your user ram anymore.

Quote
The reason I ask is that since I have upgraded to a 3GB GPU I have seen more OOM errors than before (with a 2GB GPU

That's purely coincidental or, you might have changed your settings and products used, there's no reason why having more VRAM would lead to more crashes, on a 64 bit OS.

altstiff

  • Jr. Member
  • **
  • Posts: 78
  • My F/O is a dog
    • Visit my flightsim blog..
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #2 on: November 05, 2012, 12:20:49 am »
Thanks Umberto for the quick reply (on a weekend even!).

I was always under the impression that this was the case (on 64bit systems, the GPU memory does not get mapped thru the 4GB of VAS l;ike it does on a 32bit system) but wanted to ask just to clarify.

As I said, since adding a 3GB card I am getting more OOM error warnings from FSUIPC (the gong, gong noise).

I did recently added this patch to my flight sim system (running W7 64bit)...

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

And wonder if that has anything to do with it? It should have done the opposite as I see...

virtuali

  • Administrator
  • Hero Member
  • *****
  • Posts: 41582
    • VIRTUALI Sagl
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #3 on: November 05, 2012, 12:56:15 am »
That fix is related only to the "Desktop HEAP", which is an entirely different thing of the Virtual Address Space.

The VAS is measured in GB, and it's 4GB per app on a 64 bit OS running 32 bit apps. The Desktop Heap is measured in MB and it's a storage for desktop objects like menus, icons, etc. It's possible you applied the fix in the wrong way, for a 32 bit OS, so you actually *decreased* the default value for a 64 bit OS, which is 20MB.

Check your registry and see what that fix set this value to, your link on Microsoft discusses the registry keys involved, the most important one is this:

SharedSection=1024,xxxxx,512

the xxxxx defaults to 20480 (20MB) on a 64 bit OS, be sure is not set to a lower value now.

Since this memory allocates space for cursors, icons, pens, menus, etc, if you are getting OOM because of it, it seems you are simply running too many program at the same time OR some of your addons is LEAKING GDI resources, like creating pens and not destroying properly.

altstiff

  • Jr. Member
  • **
  • Posts: 78
  • My F/O is a dog
    • Visit my flightsim blog..
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #4 on: November 05, 2012, 01:14:10 am »
It's all good there as the "fix it for me" makes sure to set the right values.

And double checking them now they are SharedSection=1024,20480,1024 (the last value is 768 by default on 64bit systems)

When looking at my VAS usage in task manager, am I looking at commit size?

« Last Edit: November 05, 2012, 04:49:03 am by altstiff »

virtuali

  • Administrator
  • Hero Member
  • *****
  • Posts: 41582
    • VIRTUALI Sagl
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #5 on: November 05, 2012, 08:53:46 am »
I suggest using Process Explorer to check for memory usage.

fls

  • Full Member
  • ***
  • Posts: 105
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #6 on: November 09, 2012, 08:31:25 pm »
Does more system ram do more for framerate at FSDT type aiports or v ram help?

Frank

virtuali

  • Administrator
  • Hero Member
  • *****
  • Posts: 41582
    • VIRTUALI Sagl
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #7 on: November 10, 2012, 12:58:08 am »
Does more system ram do more for framerate at FSDT type aiports or v ram help?

Not really, unless (because of ram exhaustion) your system is start to swap to hard drive, so rather than just low fps, you would probably see lots of pauses/stuttering. In this case, increasing ram might improve the stutters, but not the fps.

If you are having low fps, the n.1 cause it's too many AIs, so just lower the traffic density and will probably result in the bigger fps increase possible.

Paul J

  • Newbie
  • *
  • Posts: 10
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #8 on: November 15, 2012, 06:49:36 pm »
I know that on a 32bit O/S the GPU's RAM is mapped through the Virtual Address Space. On a 64bit O/S is the GPU's ram mapped the same way?

The reason I ask is that since I have upgraded to a 3GB GPU I have seen more OOM errors than before (with a 2GB GPU).

Thanks in advance

Hi Al; Yes - it's mapped that way - but your problem is likely due to the way DX9 manages graphics memory. DX9 creates a 2-gig reservation in the system memory - at least the memory is reserved - whether it's used or not. Going to a 3-gig card made the situation harder to avoid. By comparison - DX10 doesn't do this - so very few, or even zero OOM's for that reason. It's one of the reasons FSX, using DX10 is far smoother, and allows for better graphics. If you want to test this out - grab Steve's patch herehttps://dl.dropbox.com/u/52676345/DX10_Fix/shader_release_v3.1.1.zip and browse through the "How-To" doc here: https://dl.dropbox.com/u/52676345/DX10_Fix/Notes/DX10%20Notes.doc

cmpbllsjc

  • Beta tester
  • Hero Member
  • *****
  • Posts: 962
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #9 on: November 16, 2012, 08:08:50 am »
I know that on a 32bit O/S the GPU's RAM is mapped through the Virtual Address Space. On a 64bit O/S is the GPU's ram mapped the same way?

The reason I ask is that since I have upgraded to a 3GB GPU I have seen more OOM errors than before (with a 2GB GPU).

Thanks in advance

Hi Al; Yes - it's mapped that way - but your problem is likely due to the way DX9 manages graphics memory. DX9 creates a 2-gig reservation in the system memory - at least the memory is reserved - whether it's used or not. Going to a 3-gig card made the situation harder to avoid. By comparison - DX10 doesn't do this - so very few, or even zero OOM's for that reason. It's one of the reasons FSX, using DX10 is far smoother, and allows for better graphics. If you want to test this out - grab Steve's patch herehttps://dl.dropbox.com/u/52676345/DX10_Fix/shader_release_v3.1.1.zip and browse through the "How-To" doc here: https://dl.dropbox.com/u/52676345/DX10_Fix/Notes/DX10%20Notes.doc

Ok, so we have one saying that it is mapped that way on a 64bit system and Umberton saying its not, below.

I know that on a 32bit O/S the GPU's RAM is mapped through the Virtual Address Space. On a 64bit O/S is the GPU's ram mapped the same way?

Absolutely not, that's the main advantage of using a 64 bit OS, even if running just 32 bit apps: your GPU will not "steal" your user ram anymore.



So, what is the correct answer since we have two conflicting answers? I'm building a new sytem that will be on a 64bit OS and most of the choices in GPU now are 2GB and higher, but dont want to buy one that is going to cause problems if Pauls answer is correct.

virtuali

  • Administrator
  • Hero Member
  • *****
  • Posts: 41582
    • VIRTUALI Sagl
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #10 on: November 16, 2012, 11:39:59 am »
Quote
So, what is the correct answer since we have two conflicting answers? I'm building a new sytem that will be on a 64bit OS and most of the choices in GPU now are 2GB and higher, but dont want to buy one that is going to cause problems if Pauls answer is correct.

Yes, that's another thing to take into account, which is DX9 vs DX10, this is the official explanation from Microsoft:

http://support.microsoft.com/kb/940105

With a GPU with lots of VRAM, it's probably best to use DX10, if possible. Of course, 64 bit OS still has an advantage, because on a 32 bit OS, everything that is running a a certain time (including the OS itself) will be taken from the same overall shared pool of 4GB.

Paul J

  • Newbie
  • *
  • Posts: 10
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #11 on: November 16, 2012, 03:39:34 pm »
If you want to try DX10, Sean - here's a "How-To" doc - https://dl.dropbox.com/u/52676345/DX10_Fix/Notes/DX10%20Notes.doc with links to other resources within.  ;)

cmpbllsjc

  • Beta tester
  • Hero Member
  • *****
  • Posts: 962
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #12 on: November 17, 2012, 09:03:00 am »
Thanks guys.

So it's probably safe to go with a 2GB GPU on a 64bit system for FSX, but nothing more than that? I will still probably run in DX9 mode so that I dont have any compatibility issues with 3rd part addon ons. Although since I have been on XP forever and will finally be switching to an OS that is capable of trying the DX10 preview, I will probably give it a shot just to see what it looks like and how it performs.

Now that I think about it, I remember seeing a tweak mentioned in the PMDG forum that was a line you could enter in the FSX.cfg that would prevent a GPU from using more than X amount of its on board RAM. I'll have to take a look to see if I can find it.

altstiff

  • Jr. Member
  • **
  • Posts: 78
  • My F/O is a dog
    • Visit my flightsim blog..
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #13 on: November 19, 2012, 04:05:27 am »
I know that on a 32bit O/S the GPU's RAM is mapped through the Virtual Address Space. On a 64bit O/S is the GPU's ram mapped the same way?

The reason I ask is that since I have upgraded to a 3GB GPU I have seen more OOM errors than before (with a 2GB GPU).

Thanks in advance

Hi Al; Yes - it's mapped that way - but your problem is likely due to the way DX9 manages graphics memory. DX9 creates a 2-gig reservation in the system memory - at least the memory is reserved - whether it's used or not. Going to a 3-gig card made the situation harder to avoid. By comparison - DX10 doesn't do this - so very few, or even zero OOM's for that reason. It's one of the reasons FSX, using DX10 is far smoother, and allows for better graphics. If you want to test this out - grab Steve's patch herehttps://dl.dropbox.com/u/52676345/DX10_Fix/shader_release_v3.1.1.zip and browse through the "How-To" doc here: https://dl.dropbox.com/u/52676345/DX10_Fix/Notes/DX10%20Notes.doc

Thks for this Paul. Explains why I was getting OOM issues when I never got them before.

Paul J

  • Newbie
  • *
  • Posts: 10
Re: Question for Umberto about GPU RAM and 64bit O/S
« Reply #14 on: November 19, 2012, 04:06:08 pm »
A 2-gig gpu should be plenty, Sean: With less than that I have no trouble in maintaining a very solid and smooth 29.9 - 30.0 fps in the heaviest areas. My DX10 tests are usually done into the downtown core of Jon Patch's Vancouver+, with "Building Storms" or "Fair Weather", about 20/20/20 traffic with 1 airport vehicles: hundreds of circuits. I've dumped the photos now, but they were all about two - three seconds apart, and all were consistent at that frame rate. GTX 580 - 1.5 gig, not o/c'd, and a 4.9 gig 2600K, o/c in the bios. Memory is important - the best timing possible and 1T.