Disable vertical sync for glxgears

Question

Sometimes you need to check whether you Linux 3D acceleration is really working (besides the glxinfo output). This can be quickly done by the glxgears tool. However, the FPS are often limited to the displays vertical refresh rate (i.e. 60 fps). So the tool becomes more or less useless since even a software render can produce 60FPS glxgears easily on modern CPUs.

I found it rather hard to get a quick and easy solution for this, I answer my own question. Hopefully it saves your time.

score 144 · Accepted Answer · answered Jun 19 '13 at 16:09

144

The vblank_mode environment variable does the trick. You should then get several hundreds FPS on modern hardware. And you are now able to compare the results with others.

$>   vblank_mode=0 glxgears

answered Jun 19 '13 at 16:09

mschmoock

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Exactly what I was looking for. I was getting 59.984 FPS, which is the refresh rate. Setting `vblank_mode=0` I am now getting 1375.257 FPS on an old Intel i965 video driver running OpenBSD 5.6. – Clint Pachl Mar 11 '15 at 13:13
41

It's probably worth mentioning that this only works for the Mesa open-source video drivers – ali_m Apr 03 '15 at 09:00
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Works for me using Radeon/Intel hybrid with Mesa – Mark K Cowan Aug 11 '16 at 03:22
this kind of works but freezes the entire computer, requiring seperate TTY pkill on my machine (arch) – phil294 Jun 10 '18 at 05:26
vblank_mode=2 is to enable vsync and vblank_mode=1 is to disable. vblank_mode=0 also works to disable as anything else but "2". – desgua Dec 11 '21 at 09:57

ali_m · Answer 2 · 2015-04-21T20:23:32.510

101

If you're using the NVIDIA closed-source drivers you can vary the vertical sync mode on the fly using the __GL_SYNC_TO_VBLANK environment variable:

~$ __GL_SYNC_TO_VBLANK=1 glxgears
Running synchronized to the vertical refresh.  The framerate should be
approximately the same as the monitor refresh rate.
299 frames in 5.0 seconds = 59.631 FPS

~$ __GL_SYNC_TO_VBLANK=0 glxgears
123259 frames in 5.0 seconds = 24651.678 FPS

This works for me on Ubuntu 14.04 using the 346.46 NVIDIA drivers.

edited Apr 21 '15 at 20:23

answered Mar 29 '15 at 12:45

ali_m

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It also works on Ubuntu 16.04, 387.26 NVIDIA drivers. – Alejo Bernardin Jan 09 '18 at 18:42
I seem to get similar results on all my machines. They're all a little above 20 thousand FPS. Is this a limit of Nvidia cards? – Aaron Franke May 08 '18 at 00:37
I got 47 thousand FPS on a GTX1050 – drescherjm Feb 15 '19 at 03:52
It worked with 13k FPS for a GTX 1050 Ti in Ubuntu 18.04. – fegemo Mar 08 '19 at 19:02
Also works on the Jetson Nano. I get about 2650 FPS. – robotrovsky Nov 29 '19 at 19:52
Worked with 23k FPS on Debian (4.19 Linux Kernel) using nvidia-xrun with NVIDIA 1050 ti (Mobile) and 444.48.02 Nvidia drivers. I'm surprised with the 47k of our colleage drescherjm. I want to know how he did it. hahahhaha – R. W. Prado Jan 20 '20 at 19:10
In a pure doing the command "nvidia-xrun env __GL_SYNC_TO_VBLANK=0 glxgears" screen I got 24.5k FPS. I think it's not possible to get more. Well, glxgears is not a good performance test. hahahaha – R. W. Prado Jan 20 '20 at 19:25

nocnokneo · Answer 3 · 2014-10-23T12:16:07.163

For Intel graphics and AMD/ATI opensource graphics drivers

Find the "Device" section of /etc/X11/xorg.conf which contains one of the following directives:

Driver "intel"
Driver "radeon"
Driver "fglrx"

And add the following line to that section:

Option     "SwapbuffersWait"       "false"

And run your application with vblank_mode environment variable set to 0:

$ vblank_mode=0 glxgears

For Nvidia graphics with the proprietary Nvidia driver

$ echo "0/SyncToVBlank=0" >> ~/.nvidia-settings-rc

The same change can be made in the nvidia-settings GUI by unchecking the option at X Screen 0 / OpenGL Settings / Sync to VBlank. Or, if you'd like to just test the setting without modifying your ~/.nvidia-settings-rc file you can do something like:

$ nvidia-settings --load-config-only --assign="SyncToVBlank=0"  # disable vertical sync
$ glxgears  # test it out
$ nvidia-settings --load-config-only  # restore your original vertical sync setting

For Nvidia you can run `nvidia-settings --load-config-only --assign="SyncToVBlank=0"` to just change the X display's settings (and avoid modifying the config file or running the GUI). After running `glxgears` you can run `nvidia-settings --load-config-only` to restore the config settings -- which you'll probably want to do since it's a persistent setting for the running X display (i.e. not just for the shell). — Michael Krebs, Aug 25 '14 at 00:11

score 22 · Answer 4 · edited May 19 '19 at 00:53

22

Putting the other answers all together, here's a command line that will work:

env vblank_mode=0 __GL_SYNC_TO_VBLANK=0 glxgears

This has the advantages of working for both Mesa and NVidia drivers, and not requiring any changes to configuration files.

edited May 19 '19 at 00:53

Spooky

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answered May 23 '18 at 01:50

Krellan

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Works in PopOS 22.04 LTS which is based on Ubuntu 22.04 LTS !!!! – MarcoZen Feb 11 '23 at 09:20

score 7 · Answer 5 · answered Jul 11 '13 at 03:24

7

Disabling the Sync to VBlank checkbox in nvidia-settings (OpenGL Settings tab) does the trick for me.

answered Jul 11 '13 at 03:24

neutro

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score 5 · Answer 6 · answered Aug 14 '15 at 00:21

5

I found a solution that works in the intel card and in the nvidia card using Bumblebee.

> export vblank_mode=0
glxgears
...
optirun glxgears
...
export vblank_mode=1

answered Aug 14 '15 at 00:21

olmerg

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score 2 · Answer 7 · edited Jun 20 '20 at 09:12

2

For intel drivers, there is also this method

Disable Vertical Synchronization (VSYNC)

The intel-driver uses Triple Buffering for vertical synchronization, this allows for full performance and avoids tearing. To turn vertical synchronization off (e.g. for benchmarking) use this .drirc in your home directory:

<device screen="0" driver="dri2">
    <application name="Default">
        <option name="vblank_mode" value="0"/>
    </application>
</device>

edited Jun 20 '20 at 09:12

Community

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answered Nov 28 '13 at 22:12

Kevin

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This is a link-only answer. Linking to some documentation is all well and good, but not enough to constitute an answer by itself (also links die, externally-hosted pages change etc.). Could you please summarise the key points in your answer? – ali_m Mar 29 '15 at 12:54

Disable vertical sync for glxgears

7 Answers7

For Intel graphics and AMD/ATI opensource graphics drivers

For Nvidia graphics with the proprietary Nvidia driver