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[109.81.90.116]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-432bd5ee893sm3339336f8f.37.2026.01.06.01.49.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Jan 2026 01:49:29 -0800 (PST) Date: Tue, 6 Jan 2026 10:49:28 +0100 From: Michal Hocko To: Jiayuan Chen Cc: Shakeel Butt , linux-mm@kvack.org, Jiayuan Chen , Andrew Morton , Johannes Weiner , David Hildenbrand , Qi Zheng , Lorenzo Stoakes , Axel Rasmussen , Yuanchu Xie , Wei Xu , linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] mm/vmscan: mitigate spurious kswapd_failures reset from direct reclaim Message-ID: References: <20251222122022.254268-1-jiayuan.chen@linux.dev> <4owaeb7bmkfgfzqd4ztdsi4tefc36cnmpju4yrknsgjm4y32ez@qsgn6lnv3cxb> <2e574085ed3d7775c3b83bb80d302ce45415ac42@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 113218000B X-Stat-Signature: xydn5doirr9jq1tzhxhk5u6yd6jwxibc X-HE-Tag: 1767692970-902259 X-HE-Meta: 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 TuAx6ERM IqS7nPrLxtLB/sUdZC4KSVGPS8x06KbfcM7PV5jmnRGybsJqIY0k1j5nG4S4LmOO+xXDNNDxwmM54Fivow2RnaeT2MNjrJdsHdJATiQq2fPNOxZr+G9hdGSt9z+LdLE0Lcj9alJPzSc5/W6eJpKlsdQyNNArSRnT+uxAk60BlMl1/G0EgRiAQh53z4cV9qtDyf1C2piGJkePI+o8fUlhSEpmhDqNPB0tv/mMsMM34souQsAQifawuCTbokekcvoWjklYMHt3sVQWXFMPcDgPNrjilH1oV3QFTVyWrUj6uXRVVfYuJrBw/vcnC+WZ4aRs3TVSofG6XdTMu+lFTwPVHeyzItQUYgF+0HBt881JhSFQUmhv+RBlsNr0miRCdU7Igos7IAcWbSvm19TBTcqBVpc9Cpw== 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 06-01-26 05:25:42, Jiayuan Chen wrote: > That said, I believe this patch is still a valid fix on its own - resetting kswapd_failures > when the node is not actually balanced doesn't seem like correct behavior regardless of the > broader context. Originally I was more inclined to opt out memcg reclaim from reseting kswapd retry counter but the more I am thiking about that the more your patch makes sense to me. The reason being that it handles both memcg and global direct reclaims in the same way which makes the logic easier to follow. Afterall the primary purpose is to resurrect kswapd after we can see there is a better chance to reclaim something for kswapd. Until that moment direct reclaim is the only reclaim mechanism. Relying on pgdat_balanced might lead to re-enabling kswapd way much later while memory reclaim would be still mostly direct reclaim bound - thus increase allocation latencies. If we wanted to do better we would need to evaluate recent refaults/thrashing behavior but even then I am not sure we can make a good cut off. So in the end pgdat_balanced approach seems worth trying and see whether this could cause any corner cases. -- Michal Hocko SUSE Labs