20.04LTS very slow after upgrade

[Frank P]

Just did desktop version update from 18.04LTS (which was working perfectly) to 20.04 LTS
Dell xps13 laptop connecting thru Dell Docking station and an HDMI 2 port KVM switch
Boot up time seems normal. Keyboard response is making system almost unusable. Response is 4 to 5 characters behind
Other laptop on kvm switch no problem,
Any suggestions appreciated

[TheFu]

Try a fresh install.

My first 20.04 install was with the Mate DE and I selected ZFS (experimental). Everything took minutes. After fighting with it for about 30 minutes, I did another fresh install, still with Mate, but with LVM+ext4 and it was faster, though still slow by my standards.

Next I loaded my preferred window manager (no DE), verified that X11 was used, not Wayland, and re-logged in. All was crazy fast. That had solved it. I still needed to fix the terrible swap sizing and split the "root" LV after reducing it to make room for the "home" LV, but that isn't hard on a mostly empty, freshly installed system.

Extra background, probably safe to ignore:

I don't know if this was related or not, but about a month later, after my weekly patching, that system refused to boot. I wasted 30 minutes between the Advanced Grub boot, trying prior kernels, and booting from a Try Ubuntu environment to correct the boot issues by setting up a chroot and reinstalling grub. None of those things worked. If a big system problem takes more than 30 minutes to fix, I'll wipe it, do a fresh install, and restore everything from my backups. No similar problems since then ... except 20.04 does seem to require about 10G more storage than prior versions and it really, really, doesn't like it when storage is tight. I ended up adding 10G more storage. Thanks to LVM, that wasn't painful.

Here's what the storage looks like today:

$ lsblk {lots of options here; I have an alias}
NAME                       SIZE TYPE FSTYPE      MOUNTPOINT
vda                         30G disk             
├─vda1                     512M part vfat        /boot/efi
├─vda2                       1K part             
└─vda5                    29.5G part LVM2_member 
  ├─vgubuntu--mate-root     17G lvm  ext4        /
  ├─vgubuntu--mate-swap_1  4.1G lvm  swap        [SWAP]
  └─vgubuntu--mate-home     12G lvm  ext4        /home
vdb                         10G disk             
└─vdb1                      10G part LVM2_member 
  └─vgubuntu--mate-root     17G lvm  ext4        /

vdb1 is 10G and part of it was added to the "root" LV which is also on vda5.
Swap was changed from a swapfile to a swap LV. IME, swap needs to be 4.1G for all desktops. Larger isn't helpful, but less seems to not be sufficient with the bloat in modern browsers.
"home" was split off into a separate LV to make future stuff easier.

At some point in the future, I'll probably add a 40G single drive to the system and move all the current LVs over to that drive using pvmove. In theory, that could be performed while the system is running. In theory. At the same time, I should be able to have the new drive as GPT, not MSDOS and clean that part up too. As long as vda1 is still vda1 during boot with the new storage, I think it should work.

[Frank P]

I guess if all else fails I'll do a fresh install but I'm not very optimistic that will help for the following reasons.
It's running perfectly fine as long as it's not plugged in to the KVM switch. Plugged in, the keyboard response degrades.
The switch hasn't changed and the laptop was okay with 18.04LTS. Another laptop is also okay through the switch.
My guess is that it's something to do with the usb ports but I don't know how to check that.
I just remembered I can get hold of a laptop with a factory installed 20.04LTS desktop. I'll try that tomorrow.
Thanks
Frank

[TheFu]

Perhaps check that the USB settings in the BIOS are set to "Legacy"? That's all I got.

I use a 4-port KVM switch too. About once every 5 minutes, it sends a "resync" signal to the keyboard. I think this is from one of the "Y" USB connectors that has been on 15+ yrs now probably going bad. It shows up by the Scroll-Lock LED flashing on the keyboard and no inputs being accepted for that short period. My keyboard is a true IBM 101M with all the clickity noise. I'm addicted to the "feel" and have 2 spares. Best $1.50 I've spend that I can think of. Was at a used computer expo in the mid-1990s. They had hundreds of these keyboards in those metal bins just thrown in there for $0.50 each.

BTW, my Dell XPS from 2011 plugs into the KVM and is working fine. I don't use it much these days, perhaps 5 minutes a day for lite video editing. It doesn't have 20.04 on it. Until about a year ago, it was a Win7 Media Center that recorded OTA TV as the main purpose.

[Frank P]

Tried with a Levono factory installed 20.04LTS desktop; works perfectly. One difference from the Dell is that it used a different type usb port. Have ordered an adaptor for the xps13. Will see what happens.
Re keyboards, I have a "retro" with "clickable" keys that actually move, almost like a typewriter

[Frank P]

okay. everything works. Used a different USB-C port on the xps13 with a C-to-A 3.0 adapter and the keyboard delay is gone!!!!!