[Bug 204181] NULL pointer dereference regression in amdgpu

bugzilla-daemon at bugzilla.kernel.org bugzilla-daemon at bugzilla.kernel.org
Wed Aug 21 18:36:30 UTC 2019


--- Comment #38 from Sergey Kondakov (virtuousfox at gmail.com) ---
(In reply to Alex Deucher from comment #37)
> (In reply to Sergey Kondakov from comment #34)
> > By the way, is there any disadvantage in forcing TearFree to be always on
> > when it works ? Like additional frame of latency or something like that ?
> The TearFree option is there to deal with compositors that do not support
> sync to vblank. The ddx allocates another front buffer and then that buffer
> is updated synchronized with vblank with the data from the real front
> buffer.  So it uses an additional buffer.

Thanks ! It's a shame, I've already begun believing in "The Silver Bullet of
VSync". And it's completely "software" GPU-agnostic function, so alternatives
like Wayland would have to just reimplement it the same way ? It always adds a
buffer or "smart-enough" compositor can opt-out ? Or "the correct fix for
latency" with TF is disabling vsync everywhere (such as kwin's
GLPreferBufferSwap=n) else and let it handle it ?

No matter how I previously tried, nothing other than TearFree guaranteed actual
lack of tearing in all times in simple 2x1080p configuration but there is
abundance of buffering as it is in apps and a compositor + latency of LCD
displays. I'm sure, you're aware of
https://gitlab.freedesktop.org/xorg/xserver/issues/244 too. Strange that "the
magic" of TF isn't done directly in compositors or kernel then.

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