PSA: Windows 10 Now Reserves Drastically Less VRAM
outrider42
Posts: 3,679
Ah, the dreaded VRAM reservation that Windows 10 introduced. Just a heads up as this has been a topic of discussion ever since Windows 10 first released. Windows 10 has generally reserved around 15-20% of a GPU's VRAM capacity regardless of whether it was for display or not. Windows 10 2004 update changes this behavior. With this update, Windows 10 now reserves a flat 900 MB regardless of VRAM capacity.
With my 1080tis, my Daz help file used to say I had 9.1GB available. With Windows 10 2004, it now says this:
2020-09-15 22:28:59.187 Iray [INFO] - IRAY:RENDER :: 1.0 IRAY rend info : CUDA device 0 (GeForce GTX 1080 Ti): compute capability 6.1, 11.000 GiB total, 10.041 GiB available
2020-09-15 22:28:59.189 Iray [INFO] - IRAY:RENDER :: 1.0 IRAY rend info : CUDA device 1 (GeForce GTX 1080 Ti): compute capability 6.1, 11.000 GiB total, 10.039 GiB available, display attached
I now have just over 10GB on each. Horray! This should also extend to all GPUs, so the upcoming 3090 should report having about 23GB available. Of course, if any of you have a Titan RTX right now, you can test this out for yourself and see how much it reports.
This update is a large one, so make sure you set aside some time to do it. I just wanted to say this as I know some Daz users might jump on this right away seeing how much VRAM they may get out of it.
If you have updated to Windows 10 2004, feel free to post the report in your help file so we can confirm it for different GPUs. For reference, the help file is Help>Troubleshooting>View Log File. Do this right after opening up Daz Studio, scroll all the way down, and you should see the lines similar to mine near the bottom.
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Comments
Windows 10 has never used more than 0.4-0.5 Gig of the 8 Gig available VRam for me. This was true when I installed the RTX 2070 in May of last year. I'm running Win 10 V2004 now and that behaviour has not changed. It certainly is not grabbing 900 Meg.
Windows 10 uses more VRam than 7 did, but it does not just reserve an arbitrary amount of it. Windows 10 and other applications running on the OS will use the VRam they need.
Just because the log states only X amount of total VRam is available does not mean that the OS reserved the rest of it. My Daz log states that I only have 7.042 of 8GB available, but it's Daz that's reserving the additional VRAM. It needs a certain amount of VRam for the application that cannot be made available for rendering.
How sure are you it was not a recent Daz update that changed the amount of reserved VRam vs. a Windows update?
What software did you use to report that?
For starters, I did not update Daz, just Windows. Secondly, this is being discussed in other rendering forums that are not Iray.
There was considerable debate over this topic, but I have experienced the effects myself when I was unable to render a scene that I could before Windows 10 came along. This discussion also happened outside of Daz, too, with years long support tickets in Microsoft's forums. Those people were also experiencing this issue, where Windows reserved a larger portion of VRAM. It was not just Iray, many different rendering engines were reporting similar amounts of VRAM available before and after 2004 like I just did. And the users could verify this by simply creating renders that hit those marks. On a 2070 the reservation is not as noticeable, but as you go up this becomes a lot more of a problem and there is evidence of this taking more VRAM in larger and larger cards.
Also, this behavior applied to all GPUs in the system, including those not attached to a monitor.
https://www.avsim.com/forums/topic/574843-does-windows-10-2004-update-really-give-you-1gb-of-vram-back/
Here you will see people getting nearly the same numbers I did with the update, and they are not using Iray. This 100% Windows.
I have 1080tis, and the max scene I can create uses just above 9.2 GB VRAM. Anymore and it drops to CPU mode. Keep in mind this is with two 1080tis, and one is not attached to a monitor. Thus if Windows did not reserve much VRAM, then it should be able to go higher as this card has 11GB. It is over 1.5GB short, which falls in line with the percentages that everyone has said get taken out.
Here is another thread, where a user tested this with a 1060 6GB, again not attached to a monitor. The card reported 5.01 GB available. The user was able to test exactly 5.04 GB and the card was not able to allocate it.
https://stackoverflow.com/questions/47855185/how-can-i-use-100-of-vram-on-a-secondary-gpu-from-a-single-process-on-windows-1
You can find these threads all over the place. It is certainly not a Daz Iray issue, and has been well established to be a MS issue of some kind.
..bugger, I'll stay with W7 Pro for now
it says a newer version of Windows 10
I don't want to reinstall windows
I like the behaviour as it's been over a decade since I have had a video card blue screen. That used to be by far the most common type of blue screen.
I think the display driver got moved into user land, so now it doesn't blue screen when it crashes, it just gets loaded again by Windows and you blank for a second or two. The latest Windows build also has something called "Hardware-accelerated GPU scheduling" to "reduce latency and improve performance" (in Settings -> Graphics settings). There's a dev blog about it here.
Just installed the update. Vram improved from 9.011GB to 9.865.
It's intresting that you improved from 9.1 to 10.041.
Not sure why you have slightly better numbers.
Maybe because I've a 4k display?
That happened a long time ago. I foget when but when you stopped having to reboot to install a new driver.
I think that change came about with Windows 10 or soon thereafter.
I do reboot after upgrading the graphics driver, however. Maybe not right away, but after I've applied most or all of the updates I'm going to apply.
And I do notice at times that both of my Windows 10 machines will occasionally go through a "teething phase" with occasional-to-frequent bluescreens. I don't like it when that happens, but typically, after a few weeks of struggling, one day, usually after some patches, they start behaving again.
The biggest, most important thing for me is to keep my backups running. That means double-checking everything after major upgrades or disk partition reconfiguration operations, to be sure that the backups aren't inadvertently backing up a partition other than the one I intend to be backing up.
I have never EVER gotten a Windows update and I have never experienced a hardware issue (knock on wood) that was so bad that it prevented me from restoring from a backup and getting back to working order. All hail and heed my backup sermon. It's in my signature!