Re: [PATCH] Docs/mm/damon: document min_nr_regions constraint and rationale

[SeongJae Park <sj@kernel.org>]

Hello Liew,


Thank you for this patch!

On Fri, 20 Mar 2026 13:24:28 +0800 Liew Rui Yan <aethernet65535@gmail.com> wrote:

> The current DAMON implementation requires 'min_nr_regions' to be at
> least 3. However, this constraint is not explicitly documented in the
> admin-guide documents, nor is its design rationale explained in the
> design document.
> 
> Add a section in design.rst to explain the rationale: the virtual
> address space monitoring design needs to handle at least three regions
> to accommodate two large unmapped areas. While this is specific to
> 'vaddr', DAMON currently enforces it across all operation sets for
> consistency.
> 
> Also update reclaim.rst and lru_sort.rst by adding cross-references to
> this constraint within their respective 'min_nr_regions' parameter
> description sections, ensuring users are aware of the lower bound.
> 
> This change is motivated from a recent discussion [1].
> 
> [1] https://lore.kernel.org/damon/20260319151528.86490-1-sj@kernel.org/T/#t
> 
> Signed-off-by: Liew Rui Yan <aethernet65535@gmail.com>

Reviewed-by: SeongJae Park <sj@kernel.org>


Thanks,
SJ

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