As in this question: Ubuntu 17.10: high CPU usage by gnome-shell 3.26.1, and this question gnome-shell 3.26.1 constantly uses 20-30% CPU, I also have an issue where gnome-shell is constantly above 20% CPU, even with nothing other than terminal open:
$ top
....
8029 xxxxxx 20 10 1714052 601696 54568 R 46.1 15.0 1179:08 gnome-shell
....
$ lspci | grep -i vga
00:02.0 VGA compatible controller: Intel Corporation Atom Processor
Z36xxx/Z37xxx Series Graphics & Display (rev 0e)
$ glxinfo | grep -i render
direct rendering: Yes
GLX_MESA_multithread_makecurrent, GLX_MESA_query_renderer,
GLX_MESA_multithread_makecurrent, GLX_MESA_query_renderer,
Extended renderer info (GLX_MESA_query_renderer):
OpenGL renderer string: Mesa DRI Intel(R) Bay Trail x86/MMX/SSE2
GL_ARB_compute_shader, GL_ARB_conditional_render_inverted,
GL_MESA_texture_signed_rgba, GL_NV_conditional_render, GL_NV_depth_clamp,
GL_ARB_compute_shader, GL_ARB_conditional_render_inverted,
GL_NV_conditional_render, GL_NV_depth_clamp, GL_NV_light_max_exponent,
GL_OES_element_index_uint, GL_OES_fbo_render_mipmap,
I have gnome-tweak-tool installed, but I have no extensions running (I've disabled them through the menu).
Is there any way of reducing the background gnome-shell CPU usage to something sensible? At the moment I can't have a browser open, a terminal open and Dropbox syncing without the load average reaching 6+, slowing everything down.
EDIT: I've dodged the problem by logging into Unity not GNOME with Wayland or GNOME with xorg, but this is not a long-term solution, as Unity is being phased out.
Best Answer
Another solution is to upgrade all extensions (via https://extensions.gnome.org), and then to disable them one by one and see if it solves the problem. Most of the time, it comes from a faulty extension.