[Intel-gfx] [PATCH] [RFC] drm/i915: read-read semaphore optimization

[Keith Packard]

On Tue, 13 Dec 2011 14:49:49 -0800, Ben Widawsky <ben at bwidawsk.net> wrote:

> Would we want to keep domain tracking if the HW worked correctly and we
> didn't have to always flush. It seems like a shame to just gut the code
> if it actually could offer a benefit on future generations.

That sounds like premature optimization to me. If we want something
similar on future hardware, we can resurrect the old code and see what
pieces are useful. For now, we're fighting correctness and stability
issues, and given the limited (zero? negative?) performance benefits, we
just need to get to code which works reliably and provides good
performance.

The current code has gotten to the 'piles of kludges on kludges' stage,
which makes it very fragile -- see the regression caused by changing
flushing orders in the VT-d work-around.

-- 
keith.packard at intel.com
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