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

[Liew Rui Yan <aethernet65535@gmail.com>]

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?

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?

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.

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

Best regards,
Rui Yan