On 25/09/2017 18:48, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2017-09-25 16:15:42)
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
We can use engine busy stats instead of the MMIO sampling timer
for better efficiency.
As minimum this saves period * num_engines / sec mmio reads,
and in a better case, when only engine busy samplers are active,
it enables us to not kick off the sampling timer at all.
Or you could inspect port_isset(execlists.port).
You can avoid the mmio for this case also by just using HWSP. It's just
that I never enabled busy tracking in isolation, so I always ended up
using the mmio.
This would be for execlists only. I could change the main patch to do
this, you think it is worth it?
Stronger argument is that this method give more precise timing than
stochastic sampling.
v2: Rebase.
v3:
* Rebase, comments.
* Leave engine busyness controls out of workers.
v4: Checkpatch cleanup.
v5: Added comment to pmu_needs_timer change.
v6:
* Rebase.
* Fix style of some comments. (Chris Wilson)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
With a better explanation of why this is preferred,
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Thanks,
Tvrtko
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