linux-stable.git/drivers/cpuidle, branch v5.2.19

cpuidle: teo: Allow tick to be stopped if PM QoS is used

2019-10-05T11:13:31+00:00

[ Upstream commit cab09f3d2d2a0a6cb3dfb678660d67a2c3764f50 ]

The TEO goveror prevents the scheduler tick from being stopped (unless
stopped already) if there is a PM QoS latency constraint for the given
CPU and the target residency of the deepest idle state matching that
constraint is below the tick boundary.

However, that is problematic if CPUs with PM QoS latency constraints
are idle for long times, because it effectively causes the tick to
run on them all the time which is wasteful.  [It is also confusing
and questionable if they are full dynticks CPUs.]

To address that issue, modify the TEO governor to carry out the
entire search for the most suitable idle state (from the target
residency perspective) even if a latency constraint is present,
to allow it to determine the expected idle duration in all cases.

Also, when using the last several measured idle duration values
to refine the idle state selection, make it compare those values
with the current expected idle duration value (instead of
comparing them with the target residency of the idle state
selected so far) which should prevent the tick from being
retained when it makes sense to stop it sometimes (especially
in the presence of PM QoS latency constraints).

Fixes: b26bf6ab716f ("cpuidle: New timer events oriented governor for tickless systems")
Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Sasha Levin

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2019-06-19T15:09:55+00:00

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Signed-off-by: Thomas Gleixner 
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2019-06-05T15:37:16+00:00

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2019-05-30T18:29:54+00:00

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2019-05-30T18:26:37+00:00

Based on 3 normalized pattern(s):

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cpuidle: Export the next timer expiration for CPUs

2019-04-09T22:32:34+00:00

To be able to predict the sleep duration for a CPU entering idle, it
is essential to know the expiration time of the next timer.  Both the
teo and the menu cpuidle governors already use this information for
CPU idle state selection.

Moving forward, a similar prediction needs to be made for a group of
idle CPUs rather than for a single one and the following changes
implement a new genpd governor for that purpose.

In order to support that feature, add a new function called
tick_nohz_get_next_hrtimer() that will return the next hrtimer
expiration time of a given CPU to be invoked after deciding
whether or not to stop the scheduler tick on that CPU.

Make the cpuidle core call tick_nohz_get_next_hrtimer() right
before invoking the ->enter() callback provided by the cpuidle
driver for the given state and store its return value in the
per-CPU struct cpuidle_device, so as to make it available to code
outside of cpuidle.

Note that at the point when cpuidle calls tick_nohz_get_next_hrtimer(),
the governor's ->select() callback has already returned and indicated
whether or not the tick should be stopped, so in fact the value
returned by tick_nohz_get_next_hrtimer() always is the next hrtimer
expiration time for the given CPU, possibly including the tick (if
it hasn't been stopped).

Co-developed-by: Lina Iyer 
Co-developed-by: Daniel Lezcano 
Acked-by: Daniel Lezcano 
Signed-off-by: Ulf Hansson 
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki

cpuidle: exynos: Unify target residency for AFTR and coupled AFTR states

2019-04-01T21:49:51+00:00

Since commit 45f1ff59e27c ("cpuidle: Return nohz hint from
cpuidle_select()") Exynos CPUidle driver stopped entering C1 (AFTR) mode
on Exynos4412-based Trats2 board.

Further analysis revealed that the CPUidle framework changed the way
it handles predicted timer ticks and reported target residency for the
given idle states. As a result, the C1 (AFTR) state was not chosen
anymore on completely idle device. The main issue was to high target
residency value. The similar C1 (AFTR) state for 'coupled' CPUidle
version used 10 times lower value for the target residency, despite
the fact that it is the same state from the hardware perspective.

The 100000us value for standard C1 (AFTR) mode is there from the begining
of the support for this idle state, added by the commit 67173ca492ab
("ARM: EXYNOS: Add support AFTR mode on EXYNOS4210"). That commit doesn't
give any reason for it, instead it looks like it was blindly copied from
the WFI/IDLE state of the same driver that time. That time, that value
was probably not really used by the framework for any critical decision,
so it didn't matter that much.

Now it turned out to be an issue, so unify the target residency with the
'coupled' version, as it seems to better match the real use case values
and restores the operation of the Exynos CPUidle driver on the idle
device.

Signed-off-by: Marek Szyprowski 
Reviewed-by: Krzysztof Kozlowski 
Acked-by: Daniel Lezcano 
Acked-by: Bartlomiej Zolnierkiewicz 
Signed-off-by: Rafael J. Wysocki