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[34.125.238.206]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35bbad77e50sm1525460a91.6.2026.03.18.13.57.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 13:57:57 -0700 (PDT) Date: Wed, 18 Mar 2026 20:57:51 +0000 From: Bing Jiao To: Yosry Ahmed Cc: linux-mm@kvack.org, Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , David Rientjes , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , David Hildenbrand , Qi Zheng , Lorenzo Stoakes , Axel Rasmussen , Yuanchu Xie , Wei Xu , Joshua Hahn Subject: Re: [PATCH 2/3] mm/memcontrol: disable demotion in memcg direct reclaim Message-ID: References: <20260317230720.990329-1-bingjiao@google.com> <20260317230720.990329-3-bingjiao@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 35A2340010 X-Stat-Signature: 9aj61rsu5ab9pjubt3ktt6zbw7xwfpa1 X-HE-Tag: 1773867480-264472 X-HE-Meta: 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 ld5v0n6D 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Mar 17, 2026 at 04:44:34PM -0700, Yosry Ahmed wrote: > On Tue, Mar 17, 2026 at 4:07 PM Bing Jiao wrote: > > > > NUMA demotion counts towards reclaim targets in shrink_folio_list(), but > > it does not reduce the total memory usage of a memcg. In memcg direct > > reclaim paths (e.g., charge-triggered or manual limit writes), where > > demotion is allowed, this leads to "fake progress" where the reclaim > > loop concludes it has satisfied the memory request without actually > > reducing the cgroup's charge. > > > > This could result in inefficient reclaim loops, CPU waste, moving all > > pages to far-tier nodes, and potentially premature OOM kills when the > > cgroup is under memory pressure but demotion is still possible. > > > > Introduce the MEMCG_RECLAIM_NO_DEMOTION flag to disable demotion in > > these memcg-specific reclaim paths. This ensures that reclaim > > progress is only counted when memory is actually freed or swapped out. > > See the discussion @ > https://lore.kernel.org/linux-mm/20250909012141.1467-1-cuishw@inspur.com/ > and the commits/threads it is referring to. Hi Yosry, Thanks for pointing it out! I was unaware of the previous discussion regarding demotion as aging progress. I will drop patches 2 and 3 from this series and resubmit patch 1 as a standalone fix by replying to this thread. Thanks, Bing