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[109.81.92.28]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43d1e4e1c27sm63954645f8f.26.2026.04.09.03.52.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Apr 2026 03:52:53 -0700 (PDT) Date: Thu, 9 Apr 2026 12:52:52 +0200 From: Michal Hocko To: Kefeng Wang Cc: Andrew Morton , David Hildenbrand , Christian Brauner , Alexander Viro , "Matthew Wilcox (Oracle)" , Jan Kara , "Liam R. Howlett" , Lorenzo Stoakes , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH RFC] fs: drop_caches: introduce per-node drop_caches interface Message-ID: References: <20260409063503.3475420-1-wangkefeng.wang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 86F2C14000E X-Stat-Signature: 8esoyw4x9mh4tozd8gi97opzoh164sst X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1775731975-155843 X-HE-Meta: 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 g2FDFjgN yMEBE+u7BxzzkMd10Peq+di6cDYS/a5tRzyEtsJ6u6uhgkvR8+/Qm8slXjYeItyudeRRUEfAZL9U6bhw8wYfa3WNOKyxwu5CsTtfgQc3yJaQ4eKdQvmxjfqetlV0QLMg57ei0UNjxqbS/ZdqJg0qrWZFM0NPZXssMJwWxs5FErwrbGInS7MRIatCVK0+0uO8yDJqWF+nYHBpoyzFsWfUePtIhGTd1/eW5igSiMasd1AXr0JN4+tBgdxUwjyJ2cFjZgflo99oIqF5oWxtTI+smyFMvF03tp/Hgnrxxfv7cBynIKtrOqkS1fAsQeaRurkVaJyHbZpnsKrItRgYlhZg1sHfHWmQ7f6AGLRgUkDSYy4VSvR8bqyy42yT2Kg1aBKHg5gN8bdWJAs1Wc29MBlmjTmgWSw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu 09-04-26 16:54:48, Kefeng Wang wrote: > > > On 4/9/2026 4:22 PM, Michal Hocko wrote: > > On Thu 09-04-26 16:08:37, Kefeng Wang wrote: > > [...] > > > To use the reclaim interface, there are two differences, > > > > > > 1) we need to input the reclaim numbers and swappiness, this is not a big > > > problem > > > 2) for reclaim, it supports swappiness=max to only reclaim anonymous pages, > > > but cannot only reclaim file pages, > > > > Why is 2) a real constrain? > > This should not be a restriction, but a strategy. Our product wants to > migrate anonymous pages to the local instead of swapping them out. However, > the current per-node-reclaim interface does not support reclaiming only file > pages. Yes, I do understand that you want to keep your hot anonymous pages resident on some node. Those shouldn't be reclaimed by the user space triggered reclaim anyway, right? Migration will then happen during the memory offlining. This will certainly require some fine tuning but I do not see any reason this should be completely impossible. Certainly a more robust way (from API POV) than the suggested drop_caches. I am also not convinced we need page-cache-only reclaim for the existing reclaim interface. I believe it makes more sense to look at the reclaim from hotness POV rather than anon vs. file. -- Michal Hocko SUSE Labs