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In the past I have had three important applications having problems with compiz and the proprietary Nvidia graphics driver, they are; Googleearth, The Secondlife client and Blender, compiz and the old shell have come a long way and the performance of these applications when Compiz compositing is turned on is now largely acceptable.

Given that you have decided to use Compiz with Unity instead of Mutter, Will you be testing these or any other important 3d applications with Unity using Compiz and Unity Using Mutter to see which gives the best performance? Tests like these could help to make your case. so far I have only heard of the better hardware compatibility of Compiz and suspect that it will be a better compositing system for Unity.

How the above two configurations compare with the latest Compiz on the old shell and A test of Gnome Shell using its Mutter compositing running these applications would also be useful for comparison. Maybe someone at Phoronix could help in this regard if scientific presentation is desired but a honest personal experience being reported from such tests would be immensely useful I think.

I know it is early days and I do not know the status of Unity with Compiz I surely hope we will not have to go back to the old days when it was a must to turn off compositing to get work done when using certain applications,especially since the Unity shell will be more dependent on compositing than the old shell, in other words what if we have to turn off compositing to use say, Blender,what will happen?

Here is hoping that we will not have to wait another long time to get Unity/Compiz working well with applications that need 3d rendering.

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  • I have noticed that it seems you are addressing Ubuntu staff. Please notice this site is approved by Canonical, but they do not run it. The site is maintained by Stack Exchange and the people who reply here are users like you and me. Some might be developers as well, but we are mostly a community of Ubuntu users sharing experiences and helping each other. If you want a direct reply from a Canonical representative, you should contact them through the proper channels at ubuntu.com/contact-us.
    – lovinglinux
    Oct 29, 2010 at 4:23
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    This is understood but seeing so many policy related questions here I got completely carried away, still some of the above can be answered by ordinary users,Ignacio has already shown that. I do hope the Ubuntu staff read these questions, these are serious issues and we have no time for stiff necked formalities, Anyway thanks for the link.
    – Sabacon
    Oct 29, 2010 at 13:43
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    This might be better as a bug against Unity, so we can keep track of it. As far as I know, Compiz's "unredirect fullscreen windows" was disabled due to clashing with notifications and other stuff. I'd like to make it work again, so videos/3d games etc play at full speed. If you can file a bug, I can assign it to the appropriate people and we can try and fix this issue.
    – njpatel
    Nov 3, 2010 at 19:19
  • This is another "question" about Unity which doesn't seem to seek an answer. It should not matter to a USER why a design decision has been taken. Surely what matters is the USABILITY of the thing?
    – outofstep
    Nov 4, 2010 at 13:35
  • I had answered here earlier that the question is about usability, I do not know why that statement was deleted, I am all for the success of Unity, I do not agree with what you have said, a design change may affect one group positively and another negatively, which usually results in the ones affected negatively asking questions. This should indeed matter to the ones making the change and the ones negatively affected.
    – Sabacon
    May 7, 2011 at 2:50

3 Answers 3

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I don't know how it may impact some specific apps, but in my case (I have a ATI 4850), running Compiz instead of Metacity was MUCH MUCH faster. This is because the window drawing job was done by GPU instead of CPU. However, since GPU is doing something else than rendering stuff in google earth, it's performance may decrease a tiny bit. Thats why in Windows when you open a game, it disables transparencies and fancy stuff.

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  • Yes, I heard the Windows platform needs to turn off the Aero compositing system to run some 3D games properly,the Microsoft people claim they have solved this problem now, I run no Windows operating system at all so I can not prove if this is the case. Anyway, thanks for the feedback, I hope more people will understand that I am asking for feedback along these lines.
    – Sabacon
    Nov 4, 2010 at 18:16
  • Compiz doesn't actually change how the window is drawn - the individual applications are in charge of that. However, using a compositing manager such as compiz does mean that windows don't have to redraw when they get revealed (for example, by moving other windows over the top of them). Since they need to do less work, they appear faster.
    – RAOF
    Dec 9, 2010 at 20:09
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With a properly performing video card driver there should be almost no decrease in performance for regular applications. Video games running at 100 frames per second are certainly going to see a performance loss due to the extra copy and communication involved but there is no compiz-level solution for this.

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In reality, Mutter and Compiz use a similar compositing engine, so you are going to get the same kind of slowdowns on each window managers.

The only real solution to the slowdown problem is a hack which places fullscreen windows on top of our openGL scene. However this means that you can't draw notifications or anything up there since they need to be painted in the openGL scene.

We should look into exposing GEM buffer objects as FBOs directly to compiz rather than exposing them as pixmaps. This will get us the few FPS boost that we need to display those applications at full speed. This will be far in the future though.

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  • if this is true, won't using the one with lower CPU+RAM usage be the real benefit?
    – RolandiXor
    Nov 4, 2010 at 14:36
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    Thanks for the feedback,my experience using Metacity with the applications I mentioned above is that the performance was noticeably poorer than Compiz, I heard Mutter is derived from Metacity, so unless Mutter has improved over Metacity somewhat, I believe that its performance should be close to Metacity and worse than Compiz, I may be wrong though.
    – Sabacon
    Nov 4, 2010 at 18:40
  • I'm sorry, this is not true at all. In the sense that compiz and mutter are both OpenGL based composite manager you are correct in stating they are similar but beyond that they take completely different approaches. Compiz does immediate mode drawing while mutter uses clutter to put everything in a scenegraph. A scenegraph certainly makes it easier to achieve certain effects but in general and specifically in the case of clutter it is going to be slower.
    – Travis Watkins
    Dec 9, 2010 at 3:18

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