linux-kernel - Re: [RFC PATCH v2 0/3] mm/damon: Introduce node_target_mem

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Message-ID: <20260131195408.66514-1-sj@kernel.org>
Date: Sat, 31 Jan 2026 11:54:07 -0800
From: SeongJae Park <sj@...nel.org>
To: SeongJae Park <sj@...nel.org>
Cc: Ravi Jonnalagadda <ravis.opensrc@...il.com>,
	damon@...ts.linux.dev,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org,
	akpm@...ux-foundation.org,
	corbet@....net,
	bijan311@...il.com,
	ajayjoshi@...ron.com,
	honggyu.kim@...com,
	yunjeong.mun@...com
Subject: Re: [RFC PATCH v2 0/3] mm/damon: Introduce node_target_mem_bp Quota Goal Metric

On Thu, 29 Jan 2026 17:48:06 -0800 SeongJae Park <sj@...nel.org> wrote:

> On Thu, 29 Jan 2026 13:58:11 -0800 Ravi Jonnalagadda <ravis.opensrc@...il.com> wrote:
> 
> > This series introduces a new DAMON quota goal metric, `node_target_mem_bp`,
> > designed for controlling memory migration in heterogeneous memory systems
> > (e.g., DRAM and CXL memory tiering).
> > 
> > v1: https://lore.kernel.org/linux-mm/20260123045733.6954-1-ravis.opensrc@gmail.com/T/#u
[...]
>     Context 0: monitors node 0, migrate_hot -> node 1
>       goal: node_ineligible_mem_bp, nid=0, target=4000
> 
>     Context 1: monitors node 1, migrate_hot -> node 0
>       goal: node_target_mem_bp, nid=0, target=6000

In offline, Ravi enlightened me that using a single context with two schemes
instead of the above two contexts setup can be more efficienct and useful.  I
agree that.  It will be able to only single kdamond, and there could be more
flexible use cases that can use the whole-memory access pattern.

That is, we can use single context with the two schemes, but adding a core
layer DAMOS filters for applying the schemes to only memory of node 0 and node
1, respectively.  Similar for memory tiering use cases.

But I was recommending the multi contexts approach to people because the
current implementation of DAMOS is not efficient when both quota and core layer
filters are used.  I was actually working on making it improved, and just
posted an RFC patch series [1].  After the patches are merged, hopefully the
single context approach will be useful and effcient enough for varying use
cases including the memory tiering.

[1] https://lore.kernel.org/20260131194145.66286-1-sj@kernel.org

Thanks,
SJ

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