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Tue, 14 Oct 2025 03:19:16 -0700 (PDT) MIME-Version: 1.0 References: <20251013101636.69220-1-21cnbao@gmail.com> In-Reply-To: From: Barry Song <21cnbao@gmail.com> Date: Tue, 14 Oct 2025 18:19:05 +0800 X-Gm-Features: AS18NWC6N5v2tw8omBV7hBy3g3GX8bmzsyDFnwNBZ4EEXltiuUXlhijttlnObnI Message-ID: Subject: Re: [RFC PATCH] mm: net: disable kswapd for high-order network buffer allocation To: Eric Dumazet Cc: Matthew Wilcox , netdev@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Barry Song , Jonathan Corbet , Kuniyuki Iwashima , Paolo Abeni , Willem de Bruijn , "David S. Miller" , Jakub Kicinski , Simon Horman , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Yunsheng Lin , Huacai Zhou Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: yjz1183mytj1fa8guhd7e36q87qr43w9 X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: D08618000E X-HE-Tag: 1760437157-24693 X-HE-Meta: U2FsdGVkX1/tCF1N2mvvc2qNTm5/pp6R/BidW6J1tY/3c0uGxYXYxIGADaAPX5AMIwHyr+CfeiwOOglQjwQUY+dnPya8k/C/vCZ30qlQoTPTys1pbISRGrbtGZcc7VUuQW9MpnMtsJYXgrgXrOGNagXGc8P49jllmrjv/twK9jG810+YrEfIIMRaCppU6yV4qmp+3kbvNSmERHctnawT4CDz1yUgYeb4gMjZdtmWWC8RBg2gTcQ3ioh2hlv6R4oaz7FD594ahCYPZPreMakXTkAgUGpFJdwbpAIrrxj8tJI+0tVgTl8sPB6xfeS4Ka3KDtOZObEGeeKY1pHIDCSgon9gApisyzanKR5+qbQzFkMZ/qGYMcJ/RAhqznrZU8XzJd93hmFUn0x+dPbP0czC7aRdCTWlKCcee+idgCe/O+K/Bt4r6DdlJFMZvgmSDHxXjOPQXK9GKDAemtdjako76C+Nx5qYB0XQpmdvIaSj5K0npsHMfrzNEbbuB7jb41/8RGCG/2DEufxBcgXztHPVAvtHhp69+/bcVNDiYxm4/2kglhuyApKxm4sQK29IL61OFsNW/b9k3ue+GBrCxn/GrCYPshVi+TvMY9pA+HD27KvsU5Ad3UuJ+6Qkg4TGiGOfgFGCN+0J2q3XrChQ4JrUZF3V8wRS9xjZcAtBX7UP1eu0Qp3iSknFWIe+A5nLfx+PCGL7xnVZrRO5UUuJz6I8dLMX2r5wCdJBtxWPExjJWenjdab+FaOXKv6kMpXElyPVjj0ZqHgmvSNFljlYW5QkbBZX0prbn6RvrIhPBD27RTwdXcAV/cgEUr5BmGykg1jtJA65sXTpyu89LYoCqPmYJcA4Yaerno8FuKxB/kPMe1VMVbeDJZ42fQKB3T0iQh12fzisepCJNpXnQ5mfi9OGUvdoK9eIz7Nmiag3tXa/34k7pw1PZn+7X2ta4C+kmSZrDafLWA5hpK7cvNDASJb eRCDTmEE /II0GQ63iupru2T/5UBrLgFuNLZigTDWnPDvNUwbepagz4mRiAW9ii+NWzme6qH6zdHbpX8V2kxiBfY8lDQrTyh/R0Bhzcpc2a18TyNBggwKUrgOtul2h0wZvgIv+MbAYVFBJGC6k2oeofq1Np5aFG13IafaInLQtfddWv1HIiM7ST+RgnsRoa2STblNO9WYJzTyuVb0c9Fil5941bNfPdIlu1zo3Md/dsXB9Isoc1ZlBA+S6CsB6uqWwvNHpfjwvctlsTenZHbSEwI31zTZ/OQY4QwYo03tJ39WpBowy9E8MipaXSZfJA+iqIyjRa0c3yZ2Jly3zJ8PrVg5Q5usc9/bJ9AEpFT1N4cxm2puaK10aqJI6xZ5D4QPaIivIdvofCxRR 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: > > > > > > > > I think you are missing something to control how much memory can be > > > pushed on each TCP socket ? > > > > > > What is tcp_wmem on your phones ? What about tcp_mem ? > > > > > > Have you looked at /proc/sys/net/ipv4/tcp_notsent_lowat > > > > # cat /proc/sys/net/ipv4/tcp_wmem > > 524288 1048576 6710886 > > Ouch. That is insane tcp_wmem[0] . > > Please stick to 4096, or risk OOM of various sorts. > > > > > # cat /proc/sys/net/ipv4/tcp_notsent_lowat > > 4294967295 > > > > Any thoughts on these settings? > > Please look at > https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt > > tcp_notsent_lowat - UNSIGNED INTEGER > A TCP socket can control the amount of unsent bytes in its write queue, > thanks to TCP_NOTSENT_LOWAT socket option. poll()/select()/epoll() > reports POLLOUT events if the amount of unsent bytes is below a per > socket value, and if the write queue is not full. sendmsg() will > also not add new buffers if the limit is hit. > > This global variable controls the amount of unsent data for > sockets not using TCP_NOTSENT_LOWAT. For these sockets, a change > to the global variable has immediate effect. > > > Setting this sysctl to 2MB can effectively reduce the amount of memory > in TCP write queues by 66 %, > or allow you to increase tcp_wmem[2] so that only flows needing big > BDP can get it. We obtained these settings from our hardware vendors. It might be worth exploring these settings further, but I can=E2=80=99t qui= te see their connection to high-order allocations, since high-order allocations ar= e kernel macros. #define SKB_FRAG_PAGE_ORDER get_order(32768) #define PAGE_FRAG_CACHE_MAX_SIZE __ALIGN_MASK(32768, ~PAGE_MASK) #define PAGE_FRAG_CACHE_MAX_ORDER get_order(PAGE_FRAG_CACHE_MAX_SIZE) Is there anything I=E2=80=99m missing? Thanks Barry