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Question for Umberto about GPU RAM and 64bit O/S

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altstiff:
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:

--- Quote from: altstiff 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?
--- End quote ---

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
--- End quote ---

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:
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:
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:
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?

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