From: Johannes Weiner <hannes@cmpxchg.org>
To: Michal Hocko <mhocko@suse.com>
Cc: cuishiwei <cuishw@inspur.com>,
akpm@linux-foundation.org, axelrasmussen@google.com,
yuanchu@google.com, weixugc@google.com, david@redhat.com,
zhengqi.arch@bytedance.com, shakeel.butt@linux.dev,
lorenzo.stoakes@oracle.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] disable demotion during memory reclamation
Date: Tue, 9 Sep 2025 15:45:31 +0100 [thread overview]
Message-ID: <20250909144531.GA1474@cmpxchg.org> (raw)
In-Reply-To: <aL_aA2HKjfmwBaJ-@tiehlicka>
On Tue, Sep 09, 2025 at 09:40:51AM +0200, Michal Hocko wrote:
> On Tue 09-09-25 09:21:41, cuishiwei wrote:
> > When a memory cgroup exceeds its memory limit, the system reclaims
> > its cold memory.However, if /sys/kernel/mm/numa/demotion_enabled is
> > set to 1, memory on fast memory nodes will also be demoted to slow
> > memory nodes.
> >
> > This demotion contradicts the goal of reclaiming cold memory within
> > the memcg.At this point, demoting cold memory from fast to slow nodes
> > is pointless;it doesn't reduce the memcg's memory usage. Therefore,
> > we should set no_demotion when reclaiming memory in a memcg.
>
> We have discussed this in the past and it is my recollection that we
> have concluded that demotion is a part of proper aging and therefore it
> should be done during the limit reclaim.
Yes, thanks. This is intentional. Please see 3f1509c57b1b ("Revert
"mm/vmscan: never demote for memcg reclaim"") for more details.
next prev parent reply other threads:[~2025-09-09 14:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-09 1:21 cuishiwei
2025-09-09 1:36 ` Andrew Morton
2025-09-09 2:40 ` cuishiwei
2025-09-09 7:40 ` Michal Hocko
2025-09-09 14:45 ` Johannes Weiner [this message]
2025-09-10 6:36 ` cuishiwei
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