Public bug reported:
In Ubuntu 12.04 and 14.04, metacity's compositing-manager was false by default.
In 16.04, it's been set to true.
I tried to pinpoint the advantages vs the disadvantages of that, and currently
I've only seen disadvantages.
I was testing with: gsettings set org.gnome.metacity compositing-manager false
(or metacity --no-composite)
versus: gsettings set org.gnome.metacity compositing-manager true (or metacity
--composite)
Speed: the speed for window drawing and moving around is 3-5 times
slower when compositing is enabled. This is rather visible locally on
old computers, but it becomes a real problem when Xorg is used over the
network, like for example in LTSP thin clients. There, dragging around a
window draws it in slow motion a whole lot behind the mouse, like a
trail, while with compositing disabled, everything is lightning fast.
RAM: xrestop shows that with a couple of windows open, metacity now
needs 10 MB more RAM. This value increases with the number of open
windows.
Vsync: in most cases vsync was broken with or without compositing (while
with compiz it's working much better). I tried with youtube videos, with
VLC etc. The only difference I saw is that with some SDL games like
teeworlds, vsync was working with compositing disabled, and was broken
with compositing enabled.
So my personal results is that metacity's compositing-manager=true
doesn't have any advantage currently, and that it makes old client and
LTSP client performance a whole lot worse. And unfortunately those are
exactly the cases where we prefer gnome-session-flashback instead of
e.g. Unity.
Therefore I'd like to ask you to consider disabling it by default like
it was in the past.
** Affects: gnome-flashback (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1565640
Title:
Set compositing-manager=false by default
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