Re: [RFC/Discussion] mm/damon: Implementation for paused kdamond

[SJ Park <sj@kernel.org>]

On Mon, 14 Sep 2026 23:35:10 +0800 Liew Rui Yan <aethernet65535@gmail.com> wrote:

> Hi SJ,
> 
> I noticed that the current implementation for paused kdamond is
> periodically applies online parameter updates by kdamond_usleep().
> 
> I'd like to know if we should change it to waitqueue to achieve a lower
> power consumption?

I'd like to make a data driven decision :)

> 
> Previous Discussion
> ===================
> 
> I noticed that when you introduced ctx->pause [1], Sashiko asked the
> same question, and your response at the time was:
> 
>     "sample internval is 5ms by default and recommended auto-tuning
>     setup makes it hundreds of milliseconds.  So I don't think such
>     change is required."
> 
> I'm curious that, did you think it wasn't neccessary to change it to
> waitqueue when it was introduced, or it wasn't neccessary to do so even
> after it had been introduced?

I guess I thought so when the quiestion is raised.

> 
> Asussmption
> ===========
> 
> This is just my assumption, not a real use case I knew:  When 'pause' is
> set on an Android device, user might want DAMON to stop running
> completely when the screen is off, thereby reducing the load on the CPU
> without losing important information such as regions and age.
> 
> The current polling may make it harder for the phone to enter idle mode,
> resulting in some unnecessary power consumption.
> 
> However, pause feature is only present in the stable version v7.2 or
> higher, and since the latest Android kernel is 6.18, this highly
> unlikely will affect any Android users.

If whoever comes with a data that require changes, we can discuss.

> 
> [1] https://lore.kernel.org/damon/20260321202858.98091-1-sj@kernel.org


Thanks,
SJ

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