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b=fTItJmwphkdiwuwpmzrhAuNOpxlnTraGAELtElgAj72BfU7Ufj/C03C3qzZrcU7rO zO9UrfXTgGE9oucR2CVHiLGDU9bnuU9wrUFhC0oXDyaaiHcTl4fKQKP2pXQcgvMvee pwuj8ycqWx855HfKpZKql8pT5Zdn38r0Rpz6alnc= Date: Mon, 8 Sep 2025 18:36:49 -0700 From: Andrew Morton To: cuishiwei Cc: , , , , , , , , , Subject: Re: [PATCH] disable demotion during memory reclamation Message-Id: <20250908183649.da6b77d15c1076e5b69064af@linux-foundation.org> In-Reply-To: <20250909012141.1467-1-cuishw@inspur.com> References: <20250909012141.1467-1-cuishw@inspur.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 9316FA000E X-Rspamd-Server: rspam05 X-Stat-Signature: tnhx9qbtj7yiwfyrh5q3jzatd6hosose X-Rspam-User: X-HE-Tag: 1757381811-814289 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 9 Sep 2025 09:21:41 +0800 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. Is this from code inspection? Or is there some workload which benefits from this change? If the latter, please tell us all about it. > > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -6706,6 +6706,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, > .may_unmap = 1, > .may_swap = !!(reclaim_options & MEMCG_RECLAIM_MAY_SWAP), > .proactive = !!(reclaim_options & MEMCG_RECLAIM_PROACTIVE), > + .no_demotion = 1, > }; > /* > * Traverse the ZONELIST_FALLBACK zonelist of the current node to put > -- > 2.43.0