I had terrible tearing with my default Ubuntu 19.04 install last week, too. I'm using an Intel integrated GPU. The solution was to create the file /etc/X11/xorg.conf.d/20-intel.conf (and the directory, as it didn't already exist but does get checked by X11 if present) with the following content:
One's sanity is another's insanity. I dislike vsync'd desktop (and it is my #1 annoyance with Windows since 8, i just put up with it) so for me the sane option is the existing default one.
Due to responsiveness. When i move or resize a window, the UI feels too sluggish with the window (or its edge) being several frames behind the mouse cursor (which is composited by the GPU on top of the most recent framebuffer state).
Without a compositor running (which introduces its own lag due to having to draw all toplevel windows in its own backbuffer) and v-sync, everything is up-to-date.
There is tearing, of course, but the only time it bothers me is when i watch a video - in which case i enable vsync in the video player. But other than that i prefer the responsiveness.
FWIW it is the same in games too, i always play with vsync disabled and i always notice when a first person game (where i have direct control of the camera with the mouse) is rendering behind the current state (some games use previous game state(s) to keep the GPU busy). And yeah it annoys me when it happens.
Some people suggest high refreshrate monitors, but to me that feels like a workaround that lowers the problem's impact, but doesn't make the problem go away.
Is the maximum 13ms of extra latency (assuming a modest 75Hz vsync) really that noticible? With modern desktops there's got to be multiple frames of lag before you even hit the vsync?
Adaptive sync is not being used for composited desktop, only for apps that are fullscreen (i.e. no need to coordinate several different processes to random intervals).
On a similar note does anyone have any idea how to improve 4K performance with Intel graphics (i7-6600U). For me it's basically unusable as everything (even loading basic webpages like this) slows down, where as on Windows it works perfectly. For now I've downscaled to 1440p, but that isn't a great solution as now my screen is blurry. I'm using Arch, but a fresh Fedora Workstation install has the same issue.
There are similar workarounds for Nvidia and AMD cards as well. For the GeForce I used previously, I remember having to set "Force Composition Pipeline" in the nvidia-settings application. For the Radeon I'm on now, I had to do some config file magic, but I don't remember what it was anymore.
