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[109.81.16.57]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-46fb492e6ddsm250256765e9.0.2025.10.14.00.24.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Oct 2025 00:24:17 -0700 (PDT) Date: Tue, 14 Oct 2025 09:24:16 +0200 From: Michal Hocko To: Roman Gushchin Cc: Vlastimil Babka , Barry Song <21cnbao@gmail.com>, netdev@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Barry Song , Jonathan Corbet , Eric Dumazet , Kuniyuki Iwashima , Paolo Abeni , Willem de Bruijn , "David S. Miller" , Jakub Kicinski , Simon Horman , Suren Baghdasaryan , Brendan Jackman , Johannes Weiner , Zi Yan , Yunsheng Lin , Huacai Zhou , Alexei Starovoitov , Harry Yoo , David Hildenbrand , Matthew Wilcox Subject: Re: [RFC PATCH] mm: net: disable kswapd for high-order network buffer allocation Message-ID: References: <20251013101636.69220-1-21cnbao@gmail.com> <927bcdf7-1283-4ddd-bd5e-d2e399b26f7d@suse.cz> <877bwyxvvl.fsf@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <877bwyxvvl.fsf@linux.dev> X-Stat-Signature: kpe6xwebzarinat61uzibagxpjxtbjuo X-Rspamd-Queue-Id: 3CEF51C0013 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1760426659-6623 X-HE-Meta: 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 /lrPE64l MMKFr+XZor7OUuKaYApyNlgabh5T83Mc7FIy7Kfw48ock+/vz8wpw4Ni+tuyofy/thMuP/ij861wtyyEmql9J9sXrZJvekBHEOi4rSuL8fH9KQHXHBcvC4phlqGcnYaO1hDiOQpKMn7wUjoRyvpphtJIeCu51kZ6TrKl6KU127AyHEsLpaaVlhcZaHkDsjvjJeTnP080jjuXitgoaoPdtaGOx8VXkAp+zriZebKKdK/YZ8Lj6cswktjL+daUKADMeRLGm7LNOroA6CVN5ml5RSp/2HOek8idMJY57mth3jows8ngl0+zTz7esmoqeR/ImXfO6G7YDAJrgECbqt048yHepJPdYL0jLRp4eyqTLNSSqJIjwuVfsJFVkp6EX067fNTXNYvB5fCcQSTw= 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 Mon 13-10-25 15:46:54, Roman Gushchin wrote: > Vlastimil Babka writes: > > > On 10/13/25 12:16, Barry Song wrote: [...] > >> An alternative approach is to disable kswapd for these frequent > >> allocations and provide best-effort order-3 service for both TX and RX paths, > >> while removing the sysctl entirely. > > I'm not sure this is the right path long-term. There are significant > benefits associated with using larger pages, so making the kernel fall > back to order-0 pages easier and sooner feels wrong, tbh. Without kswapd > trying to defragment memory, the only other option is to force tasks > into the direct compaction and it's known to be problematic. > > I wonder if instead we should look into optimizing kswapd to be less > power-hungry? Exactly. If your specific needs prefer low power consumption to higher order pages availability then we should have more flixible way to say that than a hardcoded allocation mode. We should be able to tell kswapd/kcompactd how much to try for those allocations. -- Michal Hocko SUSE Labs