Do compositing window managers improve game performance?

[gt]

I mean, having Compiz over something like pure Openbox.

[bitcrusher]

why would it improve performance, people disable compiz when they game...

[gradinaruvasile]

Compositing managers like compiz use hardware acceleration to draw everything. Meaning they use the gpu's resources for this. Meaning that games will have to compete for the gpu's resources. Meaning that games will run slower if the compositing manager is still active.

[gt]

Originally posted by gradinaruvasile:

Compositing managers like compiz use hardware acceleration to draw everything. Meaning they use the gpu's resources for this. Meaning that games will have to compete for the gpu's resources. Meaning that games will run slower if the compositing manager is still active.

If this is the case, then does that mean simply running X Server would you the best possible performance, or are there other factors?

[blackout24]

Every modern compositing window manager unredirects fullscreen windows so your argument about it slowing down games is pretty much invalid.

[Hardtimes]

Originally posted by AbartigerNorbert:

Every modern compositing window manager unredirects fullscreen windows so your argument about it slowing down games is pretty much invalid.

Gnome Shell & Cinnamon (and mutter/muffin/clutter) still have issues with performance. They don't disable compositing and unredirect much of the time.

[UnkendTech]

in linux mint 15 MATE i take a 1 fps lost when turning compositing on vs off

[Rain Shinobi]

It's a complex debate at times. Long story short, you almost always dont want a compositor to be "compositing" your game window. Hence why most of us use "Undirect Fullscreen Windows" or similar options, so we can have all our effects but still run our games at pretty much full speed.

However it's been said, and on my machines this is my experience, if you have a decent GPU, compositing can improve your desktop performance. Or at least it feels like it. Because the GPU can help with the drawing of windows etc and takes some of the weight off the CPU.
I'm no expert though, but I think that's the basics of it. Someone can probably explain it much better or correct me.

[Fibbs]

Originally posted by AbartigerNorbert:

Every modern compositing window manager unredirects fullscreen windows so your argument about it slowing down games is pretty much invalid.

This just isn't true. Even if your compositor unredirects fullscreen windows (which not all of them do,) your desktop is still taking up graphics memory. A composited desktop takes up more memory than a none composited desktop.

The only real way around it is to launch your games in a new empty X server. By doing this the X server that contains your desktop will be shifted from graphics memory to system memory.

The amount of performance you'll gain will depend entirely on the system and the game you're trying to run. On old hardware it can be a real boost, on the latest high end gaming rig it might not be worth the effort.

[TheSniperFan]

As Fibbles already said, some have problems. KDE handles this best if you turn it on in the settings. It also has a hotkey for this so if the automatic fails, you just do it manually.
You can see some numbers in this benchmark:
http://www.phoronix.com/scan.php?page=article&item=ubuntu_1210beta_desktops&num=1

[Artemis3]

I'd rather go without compositing, which plenty of managers still do, nothing special about openbox. it's just that gnome3 (and Unity) won't; don't know if kde still supports non composited desktops. So, there is E17, XFCE, LXDE, Mate, etc, etc. Some desktop consume more ram than others, in addition to gpu if they composite. https://l3net.wordpress.com/2013/04/09/a-memory-comparison-of-light-linux-desktops-part-2/

[aliceif]

But RAM is basically a non-issue on new-ish PCs. Team Fortress 2 + KDE on my x64 ubuntu 12.04 machine with 4GB of RAM didn't even put a single MB into swap. Nor did Unity, XFCE or awesome.
For me, personally Unity's UI felt very slow at times and KDE4.10 had some lag issues, which made me switch to more lightweight DEs / WMs in the end.

[UnkendTech]

Originally posted by aliceif:

But RAM is basically a non-issue on new-ish PCs. Team Fortress 2 + KDE on my x64 ubuntu 12.04 machine with 4GB of RAM didn't even put a single MB into swap. Nor did Unity, XFCE or awesome.
For me, personally Unity's UI felt very slow at times and KDE4.10 had some lag issues, which made me switch to more lightweight DEs / WMs in the end.

i dont use swap :)

[Hardtimes]

Originally posted by Doc Holliday:

Originally posted by aliceif:

But RAM is basically a non-issue on new-ish PCs. Team Fortress 2 + KDE on my x64 ubuntu 12.04 machine with 4GB of RAM didn't even put a single MB into swap. Nor did Unity, XFCE or awesome.
For me, personally Unity's UI felt very slow at times and KDE4.10 had some lag issues, which made me switch to more lightweight DEs / WMs in the end.

i dont use swap :)

You should. Pages get tired too, you know.

[Fibbs]

Originally posted by aliceif:

But RAM is basically a non-issue on new-ish PCs. Team Fortress 2 + KDE on my x64 ubuntu 12.04 machine with 4GB of RAM didn't even put a single MB into swap. Nor did Unity, XFCE or awesome.
For me, personally Unity's UI felt very slow at times and KDE4.10 had some lag issues, which made me switch to more lightweight DEs / WMs in the end.

Your system memory is not the same as your graphics memory. Your system could have have 4GB RAM but your graphics card might only have 512MB. Your desktop uses graphics memory.

If you have 512MB graphics memory and your composited desktop takes up 80MB then you've already used 16% of the memory that your game is trying to store textures and geometry in. If a non composited desktop only uses 40MB (8%) then obviously you have more space for actual game related stuff.

As I said in my earlier post, if you're using hardware that is a few years old compositing can have a substantial impact on performance. If you're using the latest and greatest graphics card with 2GB of memory then you probably won't notice the performance hit of an 80MB composited desktop because that's only 4% of your available graphics memory.

[dilworks]

What about hybrid graphics scenarios? (nVidia Optimus: compositing desktop on Intel/Mesa, game on propietary nVidia)