Re: [PATCH] Docs/admin-guide/mm/damon/reclaim: document how to disable watermarks

[SJ Park <sj@kernel.org>]

On Wed, 28 Oct 2026 14:09:39 +0800 Jinjie Ruan <ruanjinjie@huawei.com> wrote:

> 
> 
> 在 2026/10/28 13:35, SJ Park 写道:
> > On Tue, 27 Oct 2026 22:24:24 -0700 SJ Park <sj@kernel.org> wrote:
> > 
> >> Hello Jinjie,
> >>
> >> On Wed, 28 Oct 2026 10:36:28 +0800 Jinjie Ruan <ruanjinjie@huawei.com> wrote:
> >>
> >>> DAMON_RECLAIM runs its scheme only while the free memory rate is
> >>> between `wmarks_low` and `wmarks_mid`.
> >>>
> >>> But some users want to reclaim cold pages even while the system has
> >>> plenty of free memory, and it is not obvious that the existing
> >>> watermarks parameters can already do that. So Document the setup.
> >>
> >> Thank you for this patch!
> >>
> >>>
> >>> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>

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

> >>> ---
> >>>  Documentation/admin-guide/mm/damon/reclaim.rst | 7 +++++++
> >>>  1 file changed, 7 insertions(+)
> >>>
> >>> diff --git a/Documentation/admin-guide/mm/damon/reclaim.rst b/Documentation/admin-guide/mm/damon/reclaim.rst
> >>> index ec7e3e32b4ac..23fede7d1cdb 100644
> >>> --- a/Documentation/admin-guide/mm/damon/reclaim.rst
> >>> +++ b/Documentation/admin-guide/mm/damon/reclaim.rst
> >>> @@ -193,6 +193,13 @@ DAMON_RECLAIM becomes inactive, so it does nothing but periodically checks the
> >>>  watermarks.  In the case, the system falls back to the LRU-list based page
> >>>  granularity reclamation logic.
> >>>  
> >>> +To keep DAMON_RECLAIM always active regardless of the free memory rate, set
> >>> +``wmarks_high``, ``wmarks_mid`` and ``wmarks_low`` to ``1000``, ``1000`` and
> >>> +``0``, respectively.  Then the reclamation is limited only by ``min_age`` and
> >>> +the quotas.  This is useful for reclaiming cold pages even while the system
> >>> +has plenty of free memory, e.g., right after an idle virtual machine is
> >>> +paused.
> >>> +
> >>
> >> I feel like above might be too detailed.  Particularly, the second sentence
> >> looks too detailed.  In a sense, it is not technically correct because of
> >> 'skip_anon' parameter.  We might later need to add more such controls, and I
> >> concern if this kind of detailed documentation will limit such extensions.
> >>
> >> What about keeping only the first sentence and dropping later two sentences?
> > 
> > If you don't mind, I could add this patch to damon/next after dropping the last
> > two sentences on my own.
> 
> Hi SJ,
> 
> It is fine with me, thanks. Please go ahead.

Thank you for accepting my suggestion.

I applied this patch to damon/next [1] with my suggested change.  I will repost
it for mm.git merge next week.  So, no action from your side is needed for now.
If it seems I also forgot doing that or you cannot wait for my action, please
feel free to ping me or Andrew.

[1] https://origin.kernel.org/doc/html/latest/mm/damon/maintainer-profile.html#scm-trees


Thanks,
SJ

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