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AJvYcCVKwlXwpmDnFCv4qZj7aAhje7WppPxPpOHybP1ilhgE/ui2QIV9SXjuqPK/BaYxahPxtAowqCZPSw==@kvack.org X-Gm-Message-State: AOJu0YzwlSW1dR8efrHNOG0b1w3ZgcCbGQutWMH0X2AOVuUt4Z+VtiLB uRbfMfahws66TPcqqpfHSJ0MbUSDRtVhrFEHg+HpQgzfZW2dRCvV+yjbBvdwSqRhyzM2uCX5OYb /0aoTqmX93hID/gjTG7RX7WNFmh76tno= X-Gm-Gg: AY/fxX6DPdJ/cKKzEYYLEQIKN8zBXlpPOLBavZz6OaScQUx2ZjfKWohvbvtG7q0w8Ru VEiYYAjo2KMLGs3oHh31Vt/cN5j83uvtV4qwSAQc0DQlAzDY3QqXFRBg8A9If4Jf+tx1Z15uEGl F188f5ood9egEEBOQM+dXbYjqselSn17f1BVU64oaUg57fxlmEaVJ8pOKICeATLe1nFjNkxGQ0x 3yTgXeupgGuuMcQ5SLG7faHXdBrn+1pjMH2ATpixfqYXJD941dZo7A4FsLyvF95uIBrE55loTBY zEsmb0X2AWHiWuxUf1HKzrY= X-Received: by 2002:a05:6214:19e9:b0:880:88cf:59ff with SMTP id 6a1803df08f44-8939813b73dmr21430456d6.22.1768437657315; Wed, 14 Jan 2026 16:40:57 -0800 (PST) MIME-Version: 1.0 References: <20260113081453.8293-1-akinobu.mita@gmail.com> <20260113081453.8293-4-akinobu.mita@gmail.com> In-Reply-To: From: Akinobu Mita Date: Thu, 15 Jan 2026 09:40:46 +0900 X-Gm-Features: AZwV_Qgg18kLLSG8crf76_eOaHbqkvkT03IVgWC4bh_s308ae0riyhU-hM237pI Message-ID: Subject: Re: [PATCH v4 3/3] mm/vmscan: don't demote if there is not enough free memory in the lower memory tier To: Gregory Price Cc: Michal Hocko , linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, hannes@cmpxchg.org, david@kernel.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, bingjiao@google.com, jonathan.cameron@huawei.com, pratyush.brahma@oss.qualcomm.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 43A1E100004 X-Stat-Signature: iog96xmxcpjk4k6dhezuc1mmdfw83qqg X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1768437658-151211 X-HE-Meta: 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 4lkGHTjB 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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: 2026=E5=B9=B41=E6=9C=8815=E6=97=A5(=E6=9C=A8) 2:49 Gregory Price : > > On Wed, Jan 14, 2026 at 09:51:28PM +0900, Akinobu Mita wrote: > > can_demote() is called from four places. > > I tried modifying the patch to change the behavior only when can_demote= () > > is called from shrink_folio_list(), but the problem was not fixed > > (oom did not occur). > > > > Similarly, changing the behavior of can_demote() when called from > > can_reclaim_anon_pages(), shrink_folio_list(), and can_age_anon_pages()= , > > but not when called from get_swappiness(), did not fix the problem eith= er > > (oom did not occur). > > > > Conversely, changing the behavior only when called from get_swappiness(= ), > > but not changing the behavior of can_reclaim_anon_pages(), > > shrink_folio_list(), and can_age_anon_pages(), fixed the problem > > (oom did occur). > > > > Therefore, it appears that the behavior of get_swappiness() is importan= t > > in this issue. > > "It appears that..." and the process of twiddling bits and observing > behavior does not strike confidence in this solution. > > Can you take another go at trying to define the bad interaction more > explicitly? I worry that we're modifying vmscan.c behavior to induce an > OOM for a corner case - but it will also cause another regression. I agree. It surprised me that the behavior of get_swappiness() had an impact on the issue, so I'll clarify its relationship to this issue.