https://bugs.freedesktop.org/show_bug.cgi?id=99418
--- Comment #35 from lei.pero@gmail.com --- (In reply to Michel Dänzer from comment #34)
(In reply to lei.pero from comment #33)
Yeah, but by setting 1 and using any other WM results in Chromium/Chrome being VSYNC-ed, [...]
With a compositing manager, tearing or not is up to that.
[...] i would call it mutter/clutter configuration bug [...]
vblank_mode is Mesa configuration overriding mutter's intent, so it cannot reasonably be called that.
Well, whatever it is, it affects only mutter/mutter based WM's, for now, workaround is to use vblank_mode value "1".
plus it doesn't explain DRI2 behavior that follows same standard :).
It's probably just a happy accident that it works better according to your criteria with DRI2.
Or unhappy accident for DRI3 :).