Re: Improvements and fixes for Intel ddx swap scheduling/timestamping.

[Daniel Vetter <daniel@ffwll.ch>]

On Sun, Oct 07, 2012 at 08:38:07AM +0200, Mario Kleiner wrote:
> Hi,
> 
> a series of three patches to improve the dri2 swap scheduling
> and timestamping for the current intel ddx.
> 
> The first one enables proper OML_sync_control timestamping
> while triple-buffering is enabled and XOrg 1.12+ with DRI2SwapLimit
> support is in use. So far, timestamping was unuseable with
> triple-buffering, only worked with double-buffering.
> 
> The second one repairs the broken pageflip swap scheduling, which
> is apparently in a frightening state for timing sensitive apps
> since a year, due to a tiny but really ugly bug. In a perfect
> implementation of Murphy's law, the same commit that broke the
> scheduling also disabled the builtin correctness checks that
> were supposed to catch such bugs.
> 
> The third one proposes to revert 'SwapBuffersWait' to its old
> behaviour where it didn't affect pageflipping. I just can't
> think of a case where the current behaviour makes any sense, not
> even for benchmarking? But maybe i'm overlooking something.
> 
> All patches were tested against an Intel 945-GME gpu.
> 
> I don't really care about the 'SwapBuffersWait' patch one way
> or the other, but the first two are crucial to make the intel
> ddx useable in a painless and safe way again for users of
> timing sensitive applications.

This kind of regressions suck. Are there no tests (in piglit) that check
OML buffer swap and timestamping behaviour at least internally? Or could I
volunteer you to create that? Toghether with the new kernel flip tests
this should catch any further such regressions ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch