Quoting Chris Wilson (2019-12-19 12:50:43) > Knowing the round trip time of an engine is useful for tracking the > health of the system as well as providing a metric for the baseline > responsiveness of the engine. We can use the latter metric for > automatically tuning our waits in selftests and when idling so we don't > confuse a slower system with a dead one. > > Upon idling the engine, we send one last pulse to switch the context > away from precious user state to the volatile kernel context. We know > the engine is idle at this point, and the pulse is non-preemptible, so > this provides us with a good measurement of the round trip time. It also > provides us with faster engine parking for ringbuffer submission, which > is a welcome bonus (e.g. softer-rc6). > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > Cc: Stuart Summers <stuart.summers@xxxxxxxxx> <SNIP> > +/* A simple estimator for the round-trip latency of an engine */ > +DECLARE_EWMA(delay, 6, 4) i915_delay as the minimum to emphasis that this is specific tous, with that name clarified; Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> Regards, Joonas _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
