linux-kernel - Re: [PATCH] arm64: hikey960: update idle-states

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Date:   Fri, 6 Jul 2018 09:59:15 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>, xuwei5@...ilicon.com,
        robh+dt@...nel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     leo.yan@...aro.org
Subject: Re: [PATCH] arm64: hikey960: update idle-states

On 06/07/2018 08:57, Vincent Guittot wrote:
> Update entry/exit latency and residency time of hikey960 to use more
> realistic figures based on unitary tests done on the platform.
> 
> The complete results (in us) :
>                   big cluster
>                   cluster  CPU
> max entry latency     800  400
> max exit latency     2900  550
> residency  903Mhz    5000 1500
> residency 2363Mhz       0 1500
> 
>                   little cluster
>                   cluster  CPU
> max entry latency     500  400
> max exit latency     1600  650
> residency  533Mhz    8000 4500
> residency 1844Mhz       0 1500
> 
> We can see that the residency time depends of the running OPP which is not
> handled for now. Then we also have to take into account the constraint of
> a residency time shorter than the tick to get full advantage of idle loop
> reordering(tick is stopped if idle duration is higher than tick period).
> Finally the selected residency value are :
>                  big cluster
>                   cluster  CPU
> residency            3700 1500
> 
>                   little cluster
>                   cluster  CPU
> residency            3500 1500
> 
> A simple test with a task waking up every 11,111ms shows improvement:
> - 5% a lowest OPP
> - 22% at highest OPP
> 
> The period has been chosen:
> - to be shorter than old cluster residency time and longer than new
> residency time od cluster off C-state
> - to prevent any sync with tick (4ms) when running tests that can add
> some variances between tests
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> ---

Great! Thanks for fixing the values.

Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>


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