linux-kernel - Re: [PATCH 2/2] mm/damon/sysfs-schemes: add use_nodes_of

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Message-ID: <a3f041d817534652a3e1e6545432016b@inspur.com>
Date: Thu, 29 May 2025 03:12:13 +0000
From: Simon Wang (王传国) <wangchuanguo@...pur.com>
To: SeongJae Park <sj@...nel.org>
CC: "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"hannes@...xchg.org" <hannes@...xchg.org>, "david@...hat.com"
	<david@...hat.com>, "mhocko@...nel.org" <mhocko@...nel.org>,
	"zhengqi.arch@...edance.com" <zhengqi.arch@...edance.com>,
	"shakeel.butt@...ux.dev" <shakeel.butt@...ux.dev>,
	"lorenzo.stoakes@...cle.com" <lorenzo.stoakes@...cle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "damon@...ts.linux.dev"
	<damon@...ts.linux.dev>
Subject: Re: [PATCH 2/2] mm/damon/sysfs-schemes: add use_nodes_of_tier on
 sysfs-schemes

> > This patch adds use_nodes_of_tier under
> >
> /sys/kernel/mm/damon/admin/kdamonds/<N>/contexts/<N>/schemes/<N>/
> >
> > The 'use_nodes_of_tier' can be used to select nodes within the same
> > memory tier of target_nid for DAMOS actions such as
> DAMOS_MIGRATE_{HOT,COLD}.
> 
> Could you please elaborate in what setup you think this option is useful, and
> measurement of the usefulness if you have?
> 
> I'm asking the above question because of below reasons.  My anticiapted
> usage of DAMOS_MIGRATE_{HOT,COLD} is for not only memory tiering but
> generic NUMA node management.  And my proposed usage of these for
> memory tiering is making per-node promotion/demotion for gradually
> promoting and demoting pages step by step between node.  It could be slow
> but I anticipate such slow but continued promotion/demotion is more
> important for reliable performance on production systems of large time scale.
> And I believe the approach can be applied to general NUMA nodes
> management, once DAMON is extended for per-CPU access monitoring.
> 
> I'm not saying this change is not useful, but asking you to give me a chance to
> learn your changes, better.

I believe some users may want to use only the target node's memory and reserve other nodes in the same tier for specific applications. Therefore, I added a switch file use_nodes_of_tier. I think it might be better to set the default value of use_nodes_of_tier to true (i.e., allow using fallback nodes). What do you think

> >
> > Signed-off-by: wangchuanguo <wangchuanguo@...pur.com>
> > ---
> >  include/linux/damon.h        |  9 ++++++++-
> >  include/linux/memory-tiers.h |  5 +++++
> >  mm/damon/core.c              |  6 ++++--
> >  mm/damon/lru_sort.c          |  3 ++-
> >  mm/damon/paddr.c             | 19 ++++++++++++-------
> >  mm/damon/reclaim.c           |  3 ++-
> >  mm/damon/sysfs-schemes.c     | 31
> ++++++++++++++++++++++++++++++-
> >  mm/memory-tiers.c            | 13 +++++++++++++
> >  samples/damon/mtier.c        |  3 ++-
> >  samples/damon/prcl.c         |  3 ++-
> >  10 files changed, 80 insertions(+), 15 deletions(-)
> 
> Can we please make this change more separated?  Maybe we can split the
> change for memory-tiers.c, DAMON core layer, and DAMON sysfs interface.
> That will make review much easier.

Yes,I'll split this patch to be 2 patches.


> I'll add more comments for details after above high level discussion is done.
> 
> 
> Thanks,
> SJ
> 
> [...]