Bsrgvty

I performed an upgrade from Ubuntu 18.10 to 19.04 and noticed that (somehow) creating, modifying, and deleting files is now much slower. Simply creating or deleting an empty file takes around 3 seconds on my relatively modern SSD.

Oddly enough, the commands themselves still run almost instantly:

$ time touch foo

real 0m0.003s
user 0m0.000s
sys 0m0.003s

Moreover, when I press the Enter key to execute the command, the cursor will stay on the same line during the 3 seconds. For these reasons I believe the issue is with Bash or the terminal hanging.

Similar behaviour can be seen when opening or saving files with Vim, except when running it in view mode.

EDIT
By request, I disabled all Gnome extensions, to no avail. The command ls -al ~/.local/share/gnome-shell/extensions shows that the directory is empty.

Since your issue is related to creating or deleting files, it's possible that the system's indexing/tracking activity is responsible for the delays you see.

From the release notes for Disco Dingo:

Tracker is now included by default. This allows the desktop to keep
track of recently used files and improves searching.

A graphical interface present in early versions of tracker has been removed in more recent versions, but going into Settings > Search provides an on/off switch (1 in the image below), as well as an interface to choose which folders are to be indexed (the little cog wheel icon next to 2 in the image below).

Turning Tracker on/off or adjusting its settings

Alternatively, one can use the terminal:

tracker --help points to tracker daemon and man tracker-daemon points to tracker daemon --kill as well as other options.

When I ran tracker daemon --kill, I got:

dkb@dkb-UM:~$ tracker daemon --kill
Found 3 PIDs…
 Killed process 1486 — “tracker-miner-apps”
 Killed process 1494 — “tracker-miner-fs”
 Killed process 1496 — “tracker-store”
dkb@dkb-UM:~$ pgrep -al tracker
dkb@dkb-UM:~$ 

It's quite possible that tracker hogs a lot of resources in the short term just after upgrading from a system in which tracker was not in use to 19.04 where tracker is on by default.

I came across Getting Started and First 5 minutes with Tracker which are quite simple introductory articles on tracker. If one reads those articles, it should be possible to benefit from tracker.

I have the same problem. Appears to be a bug in a gnome extension:
https://bugs.launchpad.net/ubuntu/+source/gnome-shell-extension-desktop-icons/+bug/1826604

Rename the folder of desktop-icons extension solve my problem.