linux-kernel - Re: [PATCH 0/2] mm/damon: introduce DAMOS filter type for unmapped pages

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Message-ID: <93792bf7-9507-474f-a8b0-ccd4d59742dc@sk.com>
Date: Thu, 20 Feb 2025 16:45:56 +0900
From: Honggyu Kim <honggyu.kim@...com>
To: SeongJae Park <sj@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>
Cc: kernel_team@...ynix.com, Jonathan Corbet <corbet@....net>,
 damon@...ts.linux.dev, kernel-team@...a.com, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 0/2] mm/damon: introduce DAMOS filter type for unmapped
 pages

Hi SeongJae,

On 2/20/2025 7:01 AM, SeongJae Park wrote:
> User decides whether their memory will be mapped or unmapped.  It
> implies that the two types of memory can have different characteristics
> and management requirements.  Provide the DAMON-observaibility
> DAMOS-operation capability for the different types by introducing a new
> DAMOS filter type for unmapped pages.

I asked it before at https://github.com/damonitor/damo/issues/13 about
monitoring unused paddr area but I see this patch series is related to
applying DAMOS action.

Regarding that, do you think we can skip those unused memory area using
this filter before applying DAMOS action?

I'm not sure if the current DAMOS tries pageout/migrate action for those
unused area because they are detected as cold area although those will
be imediately skiped inside action scheme.

Thanks,
Honggyu

> 
> Changes from RFC
> (https://lore.kernel.org/20241127205624.86986-1-sj@kernel.org)
> - Rebase on latest mm-unstable
> - Wordsmith commit message
> - Add documentation
> 
> SeongJae Park (2):
>    mm/damon: implement a new DAMOS filter type for unmapped pages
>    Docs/mm/damon/design: document unmapped DAMOS filter type
> 
>   Documentation/mm/damon/design.rst | 2 ++
>   include/linux/damon.h             | 2 ++
>   mm/damon/paddr.c                  | 3 +++
>   mm/damon/sysfs-schemes.c          | 1 +
>   4 files changed, 8 insertions(+)
> 
> 
> base-commit: a2130e89cbd08ddb6f023b0b10eb87ebbc67add1