OK, I did som investigation, and it seems like even for the slightest change in a window, like a cursor blink, compiz performs a fullscreen swapbuffer, and in the case of multiple monitors, compiz performs a swapbuffer that spans all the monitors.
I tried to install ccsm and disable all tweaks that could trigger this behaviour and revert to use GLX_MESA_copy_sub_buffer, but that didn't help much. Except if you start on a low resolution and change resolution to something higher. THEN compiz suddenly changes update and performs updates that are not quite that large. The only drawback is that those updates seem to cover also a number of unrelated areas that are not updated. Now needless to say this becomes very suboptimal in remoted virtual environments, and also it appears very suboptimal if llvmpipe is used. Not to mention the combination of those two... -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to compiz in Ubuntu. https://bugs.launchpad.net/bugs/1293384 Title: Compiz CPU usage dramatically increased in Ubuntu 14.04 Status in Compiz: Triaged Status in “compiz” package in Ubuntu: Triaged Bug description: It appears that the workload of low-level graphical operations used by compiz when, for example, moving windows has increased dramatically between Ubuntu 12.04 and Ubuntu 14.04. This might not be that visible when using high-end gpus, but should be clearly visible when using compiz on llvmpipe and to some-extent invalidates the approach of using compiz on top of llvmpipe as a fallback when no GPU is available: How to reproduce: 1) Use the unity-3d desktop in Ubuntu 14.04 on top of a non-accelerating Xorg driver like "modesetting". Move windows around. Note peak and average cpu-usage. How to verify compiz is the culprit: 1) copy /usr/bin/compiz from a Ubuntu 12.04 installation. Drop it in as /usr/bin/compiz on 14.04. Reboot. Perform the same window movement. CPU-usage should be substantially lower. This problem also affects VMs running on VMware ESX with a software- rendering GPU. Window movement becomes sluggish, which suggests that even with GPUs, compiz has increased the number of operations required to move windows. To manage notifications about this bug go to: https://bugs.launchpad.net/compiz/+bug/1293384/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
