Re: [PATCH 2/2] mm/damon: skip deactivated schemes in watermark checks and add fallback sleep

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

Hi SJ,

On Fri,  7 Aug 2026 07:07:39 -0700 SJ Park <sj@kernel.org> wrote:

> This is an intended implementation.
> 
> When all schemes are deactivated by watermarks, DAMON stops monitoring.  It was
> implemented in the way because we didn't want DAMON consumes system resource in
> the case.  But, later it turned out DAMON's resource consumption is really
> negligible.  Rather, it is turned out that it makes DAMON runs with stale
> history when it is activated again.  Particularly, regions have 'age' and their
> start/end addresses that was emerged before the deactivation.  Those are
> meaningless and could even cause wrong DAMOS decisions.
> 
> We don't want that anymore.  For a case the user really want DAMON completely
> stops, we introduced 'pause'.  For max_nr_snapshot-based deactivation, we don't
> intend to completely stop DAMON.
> 
> Maybe the documentation can be updated to further clarify this.

Thank you for your detailed explanation! I also glad to hear that
DAMON's monitoring's resource consumption is negligible, since I plan to
add a contexts/<N>/always_monitoring parameter later on, allowing users
to decide for themselves whether to keep monitoring even all schemes is
deactivated by watermarks.

Best regards,
Rui Yan