Video lag after updating to 19.10 from 19.04

Question

Very similar story to this person:

I updated my ubuntu 19.04 to 19.10. After the update the system lags frequently, e.g. if I hold down the right arrow in a coding program, it'll scroll for a while then pause, then continue then pause. Video conferencing is choppy, with lags every few seconds, ditto for online video.

Things I have tried:

1. Upgrade kernel to 5.5.11

2. "changed the swappiness kernel parameter to 10, and use bfq for IOSchedulers"

3. "disabling swap and using zram" (comment on same link as #2)

4. Switching from x.org to proprietary NVidia video drivers fixed the problem for Hugolpz in the above thread. I'm already using the latest version of them (440); if I change to the nouveau driver option it doesn't lag BUT: I can only have a 1024*768 output due to "xrandr: Failed to get size of gamma for output default". The solution from this thread seems to be "find and install a proper driver" which I've done... only it causes the lag problem.

5. Running an HDMI from the motherboard's video out to the monitor (instead of DP from 1080Ti). Can't see an option anywhere to select the Mobo HDMI out.

If anyone has any suggestions I'd be very grateful for thoughts and musings. I'm hoping that a clean install of 20.04 will fix things but it won't be until May for 20.04.1.

Edit: 2020-08-22 xubuntu 20.04 problem persists. GPU was tested at manufacturer for a separate issue but one might think they'd say if they found an issue. Never had a problem in windows. Been unable to watch streams or zooms smoothly for a year now, this is completely rubbish.

Answer 1

Finally got this fixed. Part of the issue is (what seems to be) a bug in Software & Updates video driver radio button code.

I built a new PC and installed xubuntu 20.04, nvidia drivers 440, same lag issue. Updated kernel from 5.4.0.42.46 to 5.8.3 with Ukuu and the res died: 1024*768, 76hz refresh, no other options, no connected displays. Software & Updates has a selected radio button for nvidia 440 still. But:

hwinfo --gfxcard
Driver Info #0:
    Driver Status: nvidiafb is not active
    Driver Activation Cmd: "modprobe nvidiafb"
  Driver Info #1:
    Driver Status: nouveau is not active
    Driver Activation Cmd: "modprobe nouveau"
  Config Status: cfg=new, avail=yes, need=no, active=unknown

Then, Selected nouveau driver, apply, hwinfo says both drivers still inactive, restarted, looks good (hi res), nvidia settings absent from start menu settings, nouveau radio button highlit in software & updates,

hwinfo --gfxcard
  Driver Info #0:
    Driver Status: nvidiafb is not active
    Driver Activation Cmd: "modprobe nvidiafb"
  Driver Info #1:
    Driver Status: nouveau is active
    Driver Activation Cmd: "modprobe nouveau"
  Config Status: cfg=new, avail=yes, need=no, active=unknown
  Attached to: #7 (PCI bridge)

So nouveau is being used, problem fixed, nvidia definitely the culprit. I'll file a bug with them / that driver team.

After posting on Nvidia, the solution (for nvidia) was to Force Full Pipeline Composition in Nvidia X Server Settings, per this.