[Bug 38800] glXSwapBuffersMscOML is slow on AMD Fusion but not on Intel 945 w/Atom

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=38800

--- Comment #33 from Simon Farnsworth <simon.farnsworth at onelan.co.uk> 2011-07-07 10:46:36 PDT ---
(In reply to comment #31)
> (In reply to comment #30)
> > So wait for bo to be idle before waiting to be out of vblank
> 
> Bad idea I'm afraid: Consider the case where the ioctl is called outside of
> vblank, but by the time the BO is idle we're in vblank. We'd need to (probably
> needlessly) wait for a full frame before the flip takes effect.

Against that, and arguing in favour of Jerome's method: if userspace is
submitting enough rendering that the BO goes idle just as vblank starts, it's
already on a performance knife-edge. We're just arguing about which way to push
you if you're already on that knife-edge.

As Jerome's method is guaranteed to at least accurately report the timestamps
of page flips, it's probably the right way to push you; I've been caught up in
other issues today, but I'll try to code up an RFC patch for Jerome's idea
tomorrow.

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