Re: [RFC PATCH] mm/damon/reclaim: allow disabling watermarks to force reclaim of cold pages

[Jinjie Ruan]

在 2026/10/20 21:58, SJ Park 写道:
> Hello Jinjie,
> 
> On Tue, 20 Oct 2026 21:32:33 +0800 Jinjie Ruan <ruanjinjie@xxxxxxxxxx> wrote:
> 
>> DAMON_RECLAIM runs its scheme only while the free memory rate is in
>> [wmarks_low, wmarks_mid].  Reclaiming cold pages raises the rate, so the
>> scheme self-stops as soon as memory looks plentiful again, which is wrong
>> for a VMM parking an idle sandbox that wants cold anonymous pages
>> reclaimed immediately.
>>
>> So add an ignore_wmarks module parameter. When set, the scheme uses
>> DAMOS_WMARK_NONE, so damos_wmark_wait_us() always returns zero and the
>> scheme stays active, bounded only by min_age and the quota.
> 
> I agree there could be use cases that doesn't want the watermarks at all.  I'd
> like to avoid adding new DAMON_RECLAIM parameters if possible, though.  That's
> becasuse DAMON_RECLAIM is introduced to let people use it without complicated
> setups.  We will of course add new parameters if really needed, but I want to
> see if there is a good alternative.
> 
> Have you considered some other alternatives?  For example, could respectively
> setting wmarks_high, wmarks_mid and wmarks_low to 100%, 100% and 0% effectively
> disable watermarks?  Have you tried that?  If that works, how about updating

Hi SJ,

Yes, it does for my use case.

> document to clearly explain the usage?  Also, have you considered using DAMON

Thank you! I will send a patch to update the doc later.

> sysfs interface instead of DAMON_RECLAIM?

DAMON sysfs can also do this with "none" watermarks. But I want the
simple DAMON_RECLAIM for only proactive reclam.

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

-- 
Best regards,
Jinjie