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

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

[Jinjie Ruan]

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.

Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 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.
+
 sample_interval
 ---------------
 
-- 
2.53.0

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

[SJ Park]

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>
> ---
>  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?


Thanks,
SJ

[...]

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

[SJ Park]

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>
> > ---
> >  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.


Thanks,
SJ

[...]

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

[Jinjie Ruan]

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>
>>> ---
>>>  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.

> 
> 
> Thanks,
> SJ
> 
> [...]

-- 
Best regards,
Jinjie

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

[SJ Park]

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

[...]