Re: [PATCH v12 3/4] cpuidle: Export the next timer/tick expiration for a CPU

On 27/02/2019 20:58, Ulf Hansson wrote:

To be able to predict the sleep duration for a CPU that is entering idle,
knowing when the next timer/tick is going to expire, is extremely useful.
Both the teo and the menu cpuidle governors already makes use of this
information, while selecting an idle state.

Moving forward, the similar prediction needs to be done, but for a group of
idle CPUs rather than for a single idle CPU. Following changes implements a
new genpd governor, which needs this.

Support this, by sharing a new function called
tick_nohz_get_next_hrtimer(), which returns the next hrtimer or the next
tick, whatever that expires first.

Additionally, when cpuidle is about to invoke the ->enter() callback, then
call tick_nohz_get_next_hrtimer() and store its return value in the per CPU
struct cpuidle_device, as to make it available outside cpuidle.

Do note, at the point when cpuidle calls tick_nohz_get_next_hrtimer(), the
governor's ->select() callback has already made a decision whether to stop
the tick or not. In this way, tick_nohz_get_next_hrtimer() actually returns
the next timer expiration, whatever origin.

Cc: Lina Iyer <redacted>
Co-developed-by: Lina Iyer <redacted>
Co-developed-by: Daniel Lezcano <redacted>
Signed-off-by: Ulf Hansson <redacted>
---

Acked-by: Daniel Lezcano <redacted>

-- 
 <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel