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Tue, 14 Oct 2025 01:58:54 -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 16:58:43 +0800 X-Gm-Features: AS18NWBgpajHqeXyjq2SfshUK90UReXA3HYugsOOoYy5fZXYwfWha3ufAj0-PzY 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: reamddt9r4yixtemcfyq3u9h8bu3zbao X-Rspamd-Queue-Id: 99605C0006 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1760432335-629536 X-HE-Meta: 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 bMGwVnkg NidE6Z+/SSH+ejgcK9oKRPsxBT0ASQxQ12Sk+txowMLv7Fzxrfb+C4/sV98K/SF72adsE4qHorkomCtQnhoO8L+tU1knubN/ARv6DrL0VyV5Cj8NR0b8WJDXVUIRX+z+oREd275OwKbRkpdomg9YM9DkwmjdwREVPWYSiUOKi5mOvhXZxvSX1HXbx2AqyodLVAZlEm1+s3aC/H5j7FKFtaEdwRejwKLj7jAflnD2hYGx/EmZL39zOleX37Ozlssq8AEChnMQvpdpK9wKZEXBTANYow1688kfhYWpab5aMcgXFZPiuJ7oSbATxKtbmDl0aa+nXZL3f1Ppqf4FJajUFU+/wt+NBx7qS+uvfoQ4B5n+AZEWBBERPH2XSUEahy4PbbELec5E4k9/wnFbkYgm/St1mT6gYEjjienE3MrPwmSPs2uoVwbFAmvu3KuCbhwYlvFsBAQnhL1+Eg3ixW1zTEzPZWQ== 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, Oct 14, 2025 at 1:04=E2=80=AFPM Eric Dumazet = wrote: > > On Mon, Oct 13, 2025 at 9:09=E2=80=AFPM Barry Song <21cnbao@gmail.com> wr= ote: > > > > On Tue, Oct 14, 2025 at 5:56=E2=80=AFAM Matthew Wilcox wrote: > > > > > > On Mon, Oct 13, 2025 at 06:16:36PM +0800, Barry Song wrote: > > > > On phones, we have observed significant phone heating when running = apps > > > > with high network bandwidth. This is caused by the network stack fr= equently > > > > waking kswapd for order-3 allocations. As a result, memory reclamat= ion becomes > > > > constantly active, even though plenty of memory is still available = for network > > > > allocations which can fall back to order-0. > > > > > > I think we need to understand what's going on here a whole lot more t= han > > > this! > > > > > > So, we try to do an order-3 allocation. kswapd runs and ... succeeds= in > > > creating order-3 pages? Or fails to? > > > > > > > Our team observed that most of the time we successfully obtain order-3 > > memory, but the cost is excessive memory reclamation, since we end up > > over-reclaiming order-0 pages that could have remained in memory. > > > > > If it fails, that's something we need to sort out. > > > > > > If it succeeds, now we have several order-3 pages, great. But where = do > > > they all go that we need to run kswapd again? > > > > The network app keeps running and continues to issue new order-3 alloca= tion > > requests, so those few order-3 pages won=E2=80=99t be enough to satisfy= the > > continuous demand. > > These pages are freed as order-3 pages, and should replenish the buddy > as if nothing happened. Ideally, that would be the case if the workload were simple. However, the system may have many other processes and kernel drivers running simultaneously, also consuming memory from the buddy allocator and possibly taking the replenished pages. As a result, we can still observe multiple kswapd wakeups and instances of over-reclamation caused by the network stack=E2=80=99s high-order allocations. > > 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 # cat /proc/sys/net/ipv4/tcp_mem 131220 174961 262440 # cat /proc/sys/net/ipv4/tcp_notsent_lowat 4294967295 Any thoughts on these settings? Thanks Barry