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AJvYcCV3hNt5t5mmc40mcCxtvMI//+y6zJvj5k/aVWTPGYT2k6Sfts4MjqDHGQU+YywKzAx2nMeEvayDjg==@kvack.org X-Gm-Message-State: AOJu0YydojRvNCD7rsXHxf2ikLqNERgEjN5JO8ntz+P2umPfL0BA2I8H g2aZOBuClLRfaxH3juV8e2ixK+KtnUkjOzgjJHnBphgMAWrb0eafaL0I6FzSeypm5gt9/TAkHDQ wCjzLViSVO7/lZu+QRda9INaRl5seN1NkzlZNsOBq X-Gm-Gg: ASbGncs9FQLvniMtvW6maekiIdm4iVPZBJ1lxrMu2s+94ybGATYEKf9cx5rN8A7t8zH 3X4vXlHDAdJWc1ABtZQZF9zS9T6UiRj/d7tIIomDcNOfOipkRiJ0ZQ5p4nbhNqxz/JQP4kBLgO7 WiteP7wd8dEImF+ZEOqlrCWb2icwe0aTAFqpKomg9ywldpYGHnoNklMNZCwZbmOZPnyABPP8+o/ UelgkiRfk4WKwOtK9KNWhof6/BAnJjQLg2YE82jBBU= X-Google-Smtp-Source: AGHT+IHR7KeqfX1q4j3neFi7CD60ffHHvOgtSgSkxcg1JbCbIReg3SIb3TKWDF50WzB6YocPrnOGpWynAn63FWdOqTE= X-Received: by 2002:a05:6214:2622:b0:820:a83:ead3 with SMTP id 6a1803df08f44-87b21032994mr371828316d6.23.1760425278145; Tue, 14 Oct 2025 00:01:18 -0700 (PDT) MIME-Version: 1.0 References: <20251014035846.1519-1-21cnbao@gmail.com> In-Reply-To: From: Eric Dumazet Date: Tue, 14 Oct 2025 00:01:07 -0700 X-Gm-Features: AS18NWD5ciaHerlqKb1LSkLizTAcEH7y8M_BZABcYRSz9LQQyJTFiKiNPr9pVjc Message-ID: Subject: Re: [RFC PATCH] mm: net: disable kswapd for high-order network buffer allocation To: Barry Song <21cnbao@gmail.com> Cc: corbet@lwn.net, davem@davemloft.net, hannes@cmpxchg.org, horms@kernel.org, jackmanb@google.com, kuba@kernel.org, kuniyu@google.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linyunsheng@huawei.com, mhocko@suse.com, netdev@vger.kernel.org, pabeni@redhat.com, surenb@google.com, v-songbaohua@oppo.com, vbabka@suse.cz, willemb@google.com, zhouhuacai@oppo.com, ziy@nvidia.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 92AE820011 X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: kctjpqzasjuhwu41bp4qt6swxqkwar84 X-HE-Tag: 1760425279-42013 X-HE-Meta: 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 OQy8FcSl F5OBPLztwufU27OiS4eQDslM5d9UCsBB7BqXH7/O47k+zu/dnAPT6Dhjg/l/tLwJaYzyyRVpYaXGQnWeUjZpZ0F0tPUaBAX4UxFY2sn1Fz0nureZUF6PzdTGLBz/jZI96QLf0qkaQTgGxN3ej8DT+bg+t99ZO0tWiqdDBWvve2oFEdgmpy3VymrgeEnQ9v+hSAj/lgEQsPc5Q8pyAivYOjfM/4cZBXJMnw6XV 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, Oct 13, 2025 at 11:43=E2=80=AFPM Barry Song <21cnbao@gmail.com> wro= te: > > > > > > > A problem with the existing sysctl is that it only covers the TX path= ; > > > for the RX path, we also observe that kswapd consumes significant pow= er. > > > I could add the patch below to make it support the RX path, but it fe= els > > > like a bit of a layer violation, since the RX path code resides in mm > > > and is intended to serve generic users rather than networking, even > > > though the current callers are primarily network-related. > > > > You might have a buggy driver. > > We are observing the RX path as follows: > > do_softirq > taskset_hi_action > kalPacketAlloc > __netdev_alloc_skb > page_frag_alloc_align > __page_frag_cache_refill > > This appears to be a fairly common stack. > > So it is a buggy driver? No idea, kalPacketAlloc is not in upstream trees. It apparently needs high order allocations. It will fail at some point. > > > > > High performance drivers use order-0 allocations only. > > > > Do you have an example of high-performance drivers that use only order-0 = memory? About all drivers using XDP, and/or using napi_get_frags() XDP has been using order-0 pages from the very beginning.