Why is my Windows application/game capped at 30FPS when running on an Intel GPU?

Question

I'm working on a fullscreen Windows desktop application that's moderately graphics-intensive, it uses OpenGL but only renders 2D content. Nothing fancy, mostly pushing pixels to the screen (up to 4K, single monitor) and uploading textures. We're using VSync to control the rendering framerate, ie. calling SwapBuffers() at the end of rendering to block until the next VBlank.

The main requirement we have is that the app runs at a solid 60FPS as it's used with a touchscreen, and interactions need to be as fluid as possible.

Because it's pretty basic, the app runs just fine on a 8th gen Intel i7 CPU with integrated Intel HD Graphics 630 GPU. Neither the CPU or GPU are anywhere near peak usage, and we can see that we're hitting a comfortable 60FPS through our in-app FPS meter. I also have it running with similar results on my Surface Book 2 with Intel i7 and integrated Intel UHD Graphics 620 GPU.

However, what I've recently started noticing is that the app sometimes starts dropping to 30FPS, then staying there either for long periods of time or sometimes even permanently. Through our FPS meter, I can tell that we're not actually spending any time rendering, it's just our SwapBuffers() call that blocks arbitrarily for 2 frames, capping us at 30FPS. The only way to get back to 60FPS is to alt-tab with another app and back to ours, or simply bringing the Windows menu up then going back to the app.

Because of the app going back to 60FPS afterwards, I'm positive that this is an intended behavior of the Intel driver, probably meant for gaming (gamers prefer a stable 30FPS rather than irregular/occasional dropped frames which make the game look choppy).

However in our case, dropping an occasional frame isn't a big deal, however being capped at 30FPS makes our UI and interactions far less pleasing to the eye, especially when it could easily render at a smooth 60FPS instead.

Is there any way to switch the driver behavior to prefer pushing 60FPS with occasional drops rather than capping at 30FPS?

Answer 1

OK so I was able to figure this out with a little bit of tweaking and reverse-engineering: The answer is that yes this is an intended but unfortunate default behavior of the Intel driver, and it can be fixed via the Intel HD Graphics Control Panel app if available, or directly in the registry otherwise (which is the only way to fix the issue on the Surface Book and other Surface devices, where the custom Intel driver doesn't expose the Intel HD Graphics Control Panel app anymore).

Starting with the simple solution: In the Intel HD Graphics Control Panel app, go to "3D", then "Application Settings". You'll first need to create an application profile, by selecting the file on disk for the process that creates the OpenGL window. Once that's done, the setting you want to adjust is "Vertical Sync". By default, "Use Application Default Settings" is selected. This is the setting that causes the capping at 30FPS. Select "Use Driver Settings" instead to disable that behavior and always target 60FPS:

This should've been pretty obvious, if it wasn't for Intel's horrible choice of terms and incomprehensible documentation. To me it looks like the choices for the settings are inverted: I would expect the capping to happen when I select "Use Driver Settings", which then implies the driver is free to adjust buffer swapping as it sees fit. Similarly, "Use Application Default Settings" implies that the app decides when to push frames, which is precisely the opposite of what the setting does. Even the little help bubbles in the app seem to contradict what these settings do...

ps: I'll post the registry-based solution in a separate answer to keep it short

Answer 2

Here is the registry-based answer, if your driver does not expose the Intel HD control panel (such as the driver used on the Surface Book and possibly other Surface laptops), or if you want to make that fix programmatically via regedit.exe or the Win32 API:

The application profiles created by the Intel HD control panel are saved in the registry under HKCU\Software\Intel\Display\igfxcui\3D using a key with the process file name (e.g. my_game.exe) and a REG_BINARY value with a 536-byte data blob divided like this:

• Byte 0-3: Anisotropic Filtering (0 = use app default, 2-10 = multiplier setting)
• Byte 4-7: Vertical Sync (0 = use app default, 1 = use driver setting)
• Byte 8-11: MSAA (0 = use app default, 1 = force off)
• Byte 12-15: CMAA (0 = use app default, 1 = override, 2 = enhance)
• Byte 16-535: Application Display Name (wide-chars, for use in the control panel's application list)

Note: all values are stored in little-endian

In addition, you need to make sure that the Global value under the same key has its first byte set to 1, which is a sort of global toggle.(the control panel sets it to 1 when one or more entries are added to the applications list, then back to zero when the last entry is deleted from the list).

The format of value is also a REG_BINARY value with 8 bytes encoded like this:

• Byte 0-3: Global toggle for application entries (0 = no entries, 1 = entries)
• Byte 4-7: Application Optimal mode (0 = enabled, 1 = disabled)

For example: