(In reply to comment #93)
> The bad part is - while before I've been getting 3.7Mchar/s in x11perf
> -aa10text - now it's like 1.3Mchar/s  so significantly slower.

That's the sacrifice, we have to stop sending commands to the GPU and
wait for it complete those in flight (quite frequently). Or else new
rectangles overwrite vertex entries still being used by later entries

> So the question here would be - isn't the corruption based on  triangle
> surface size ? So i.e. GPU is able to  process a lot of small ones - but has
> bug with bigger ones ?
> 
> Maybe a cheap test would be to flush when some longer triangle edge is
> pushed in ?

Not really, you have to predict when a VUE being used by the end of the
pipeline will be overwritten by a new rectangle at the start of the
pipeline. This is completely internal state - the primitive command we
want to feed to the GPU can contains thousands of rectangles. Instead of
counting rectangles, you want to start counting fragments (actually
texel reads since that will be the ratelimiting factor) and flush if we
queue up too much work for the GPU. If you also model how fast the gpu
is retiring fragments so that you can predict how much work is in
flight, you could further reduce flushes...

We still need to stop the gpu and wait for it to complete. No matter how
finely you do it, it will sacrifice throughput and latency.

It's a workaround. I still live in hope that after all these years we
missed some configuration detail required for gen4.

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You received this bug notification because you are a member of Ubuntu-X,
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https://bugs.launchpad.net/bugs/1098489

Title:
  [gen4] Corruption in Chrome omni bar results using Intel SNA

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