I run Ubuntu 18.04 on a modern Toshiba laptop without problems – until updating on Apr 26 2019. It needed restart. After that Gnome opened windows terribly slowly. I removed all Gnome extensions, ran sudo apt update, sudo apt autoremove, sudo apt full-upgrade, but no difference. Is this a virus? Help!? I am a near-80 astrophysicist but an Ubuntu dud and appreciate help…
Addition Apr 29: other posts made me look at dmesg. At its end:
[211509.868273] [drm:intel_pipe_update_end [i915]] ERROR Atomic update failure on pipe A (start=458201 end=458202) time 207 us, min 1073, max 1079, scanline start 1069, end 1083
[212774.344829] perf: interrupt took too long (22682 > 22655), lowering kernel.perf_event_max_sample_rate to 8750
Are these meaningful?
Addition May 6 2019: getting desperate. Top shows that the machine runs fine. Booting with my original installer 18.04 USB stick does not have the problem. I tried the previous kernel: same problem. I tried login with Gnome from Xorg: same problem. May be not a Gnome problem because other things are very slow too, Ethernet by a factor 5-10. I presume one of the many packages I installed does this after the update? – but how find it?
Best Answer
Answering my own question after 3 weeks of despaired search and a fruitless complete 18.04 reinstall including all packages I had before. Finally diagnosed and repaired by an expert family member inspired by question 1021748.
The ondemand CPU governor switched to "powersave" mode after booting up. This lowered the CPU frequency to even below the minimum set frequency of 400MHz, and stayed there hovering around 380Mhz (inspected via lscpu).
This happened when the governor switched the CPU to powersave mode:
Switching the CPU governor to performance mode solved the problem (for policy0-3):
Permanently removing the ondemand governor, made this survive reboot, keeping the governor set to performance:
No idea why the powersave mode turns out so bad and what went wrong where in the April 26 18.04 update and is still present in the reinstalled version. Some posts hint that the ondemand governor doesn't play well with the Intel pstate scaling driver... Anyhow, my question wrongly asked about gnome (I took it out). It was the CPU control affecting everything.