Activities overview causes increased CPU in Wayland & Xorg

[Daniel van Vugt]

gnome-shell CPU usage doubles when in activities overview

[Daniel van Vugt (vanvugt)]

Without the overview.

[Daniel van Vugt (vanvugt)]

With the overview.

[Daniel van Vugt (vanvugt)]

Gnome 3.28.0: without the overview

[Daniel van Vugt (vanvugt)]

Gnome 3.28.0: with the overview.

[Daniel van Vugt (vanvugt)]

Here are some realtime profiles showing gnome-shell's CPU going from 11.2% normally to 18.2% when in overview:

[Daniel van Vugt (vanvugt)]

OK it looks like the increase in CPU in activities overview is just expected. Mutter/Gnome Shell is fairly inefficient to start with so switching to a mode where it has to render more widgets and more detail of course incurs higher CPU.

I think a holistic approach is required. Not just fixing this bug, but to reduce CPU usage in all scenarios such that a 60% increase doesn't hurt so much.

[Daniel van Vugt (vanvugt)]

Looks like a 100% increase (CPU doubles) now that I'm using the trick of turning off seconds in the panel clock.

[Daniel van Vugt (vanvugt)]

I made a solid attempt at fixing a few related issues,

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/73

but failed to address this bug completely. That said, it does provide a significant absolute performance improvement to the overview.

I think this bug will be deferred indefinitely until we can make Clutter (in mutter) fundamentally more efficient as outlined in the above link.

[Daniel van Vugt (vanvugt)]

Maybe in the previous comment was being overly harsh on myself and gnome-shell. According to the latest stats, this bug was actually mostly fixed by:

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/73

which is also in Ubuntu 18.04 and later already.

So let's call this bug closed and open a new one when/if new stats are at hand.