Messages in this thread |  | | Date | Thu, 5 Apr 2018 14:47:57 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v9 10/10] cpuidle: menu: Avoid selecting shallow states with stopped tick |
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On Wed, Apr 04, 2018 at 10:50:36AM +0200, Rafael J. Wysocki wrote: > + if (tick_nohz_tick_stopped()) { > + /* > + * If the tick is already stopped, the cost of possible short > + * idle duration misprediction is much higher, because the CPU > + * may be stuck in a shallow idle state for a long time as a > + * result of it. In that case say we might mispredict and try > + * to force the CPU into a state for which we would have stopped > + * the tick, unless the tick timer is going to expire really > + * soon anyway.
Wait what; the tick was stopped, therefore it _cannot_ expire soon.
*confused*
Did you mean s/tick/a/ ?
> + */ > + if (data->predicted_us < TICK_USEC) > + data->predicted_us = min_t(unsigned int, TICK_USEC, > + ktime_to_us(delta_next)); > + } else { > + /* > + * Use the performance multiplier and the user-configurable > + * latency_req to determine the maximum exit latency. > + */ > + interactivity_req = data->predicted_us / performance_multiplier(nr_iowaiters, cpu_load); > + if (latency_req > interactivity_req) > + latency_req = interactivity_req; > + } > > expected_interval = data->predicted_us; > /* >
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