AMDGPU DC Code Improvements Bring Better Page-Flipping

[phoronix]

Phoronix: AMDGPU DC Code Improvements Bring Better Page-Flipping

The once notorious AMDGPU "DC" code (formerly known as DAL) saw a fresh round of patches on Tuesday further improving this display stack shared between the Windows and Linux drivers for advanced functionality from FreeSync to HDMI/DP audio and much more...

http://www.phoronix.com/scan.php?page=news_item&px=AMDGPU-DC-Better-Flipping

[oleid]

Anyone with DC problems, too? Since DC is merged, I only get black screen (on my 4k screen) during boot. I can disable DC, and then command line works. But well...

[Mangix]

Nope. Nothing but benefits. I updated the kernel on elementaryOS from the stupid non-LTS 4.15 that they have to 5.0 and was amazed at how much more performance I now get.

[tildearrow]

I have a question only partially related to page-flipping.

Is it possible to disable Adaptive-VSync in Mesa? It seems to be always on and I've been unable to find a way to disable it... (by this I do not mean Adaptive-Sync AKA FreeSync, but rather the technique that disables VSync if the game is running too slow by not waiting for VBlank when swapping but rather doing so on the next command)

[xception]

I have a question only partially related to page-flipping.

Is it possible to disable Adaptive-VSync in Mesa? It seems to be always on and I've been unable to find a way to disable it... (by this I do not mean Adaptive-Sync AKA FreeSync, but rather the technique that disables VSync if the game is running too slow by not waiting for VBlank when swapping but rather doing so on the next command)

I believe it's vblank_mode=0 before the commandline.
just "glxgears" as command gives me "301 frames in 5.0 seconds = 60.001 FPS"
while "vblank_mode=0 glxgears" outputs after a warning "101447 frames in 5.0 seconds = 20289.314 FPS"
There is a second switch in xorg.conf, for the old radeon driver it was:
Option "swapbufferswait" "0"
I don't know what the equivalent is for amdgpu or if it's needed at all
you can add vblank_mode=0 to your environment so all applications start in that mode if you prefer

[Peter Fodrek]

Anyone with DC problems, too? Since DC is merged, I only get black screen (on my 4k screen) during boot. I can disable DC, and then command line works. But well...

Only trouble was since I was started to us kernel 4.20 : It take 15 seconds since display manager service was started till displaying mouse cursor and one minute form display mouse cursor till lightdm was displayed. But wait I am just dooing

sudo zypper dup

with

kernel-default 4.20.3-2.1.g4b478de -> 4.20.3-3.1.g4ac37bd
kernel-default-devel 4.20.3-2.1.g4b478de -> 4.20.3-3.1.g4ac37bd
kernel-devel 4.20.3-2.1.g4b478de -> 4.20.3-3.1.g4ac37bd
kernel-syms 4.20.3-2.1.g4b478de -> 4.20.3-3.1.g4ac37bd


It may help me or not?

[tomtomme]

Anyone with DC problems, too? Since DC is merged, I only get black screen (on my 4k screen) during boot. I can disable DC, and then command line works. But well...

Yup, one problem. I have this bug https://bugzilla.kernel.org/show_bug.cgi?id=201795
I still am at kernel 4.14 because of it.

[Azpegath]

It's a shame it doesn't get into 5.0, it would be nice to have some clean-ups of the DC as soon as possible. I agree with oleid, there has been many stability issues with DC. I'm running it on a R290, so I guess I'm an outlier (they aren't officially supported, right?) and have to accept some issues, but the kernel didn't even boot for 2 whole main release versions. Now they've fixed the first specific issue I had, but I still haven't tried updating to anything newer than 4.18.20, since there where so many other issues (the filesystem corruption, etc). I think I'm mainly waiting for 5.0.(>5), to not risk hitting any issues.

[Azpegath]

Yup, one problem. I have this bug https://bugzilla.kernel.org/show_bug.cgi?id=201795
I still am at kernel 4.14 because of it.

I read through your bug report, and perhaps you are able to speed up the process by bisecting the issue. I know it's a hassle to constantly rebuild the kernel and reboot (I've done it once, and am not longing to do it again), but it will help the devs a lot. Have you tried bisecting before, or would you like some info on it?

[xception]

It's a shame it doesn't get into 5.0, it would be nice to have some clean-ups of the DC as soon as possible. I agree with oleid, there has been many stability issues with DC. I'm running it on a R290, so I guess I'm an outlier (they aren't officially supported, right?) and have to accept some issues, but the kernel didn't even boot for 2 whole main release versions. Now they've fixed the first specific issue I had, but I still haven't tried updating to anything newer than 4.18.20, since there where so many other issues (the filesystem corruption, etc). I think I'm mainly waiting for 5.0.(>5), to not risk hitting any issues.

I also have a R9 290, I use amdgpu.dc=0 on kernel commandline because DC forces my display in 1080p and with it disabled I can get 4K resolution