[Intel-gfx] Improvements and fixes for Intel ddx swap scheduling/timestamping.

[Eric Anholt]

Daniel Vetter <daniel at ffwll.ch> writes:

> 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 ...

I posted a first couple of tests that try to just hit the API for the
most part, but I don't test the MSCs or wall-time timing behavior.
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