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[34.48.33.21]) by smtp.gmail.com with UTF8SMTPSA id 00721157ae682-7943af1443dsm678977b3.2.2026.01.22.11.42.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Jan 2026 11:42:58 -0800 (PST) Date: Thu, 22 Jan 2026 14:42:57 -0500 From: Willem de Bruijn To: Willem de Bruijn , Eric Dumazet , Jakub Kicinski Cc: Srujana Challa , Willem de Bruijn , netdev@vger.kernel.org, virtualization@lists.linux.dev, pabeni@redhat.com, mst@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, andrew+netdev@lunn.ch, davem@davemloft.net, ndabilpuram@marvell.com, Willem de Bruijn Message-ID: In-Reply-To: References: <20260122091527.339180-1-schalla@marvell.com> <20260122075206.504ec591@kernel.org> Subject: Re: [PATCH net-next] virtio_net: Increase RSS max key size to match NETDEV_RSS_KEY_LEN Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Willem de Bruijn wrote: > Eric Dumazet wrote: > > On Thu, Jan 22, 2026 at 4:52=E2=80=AFPM Jakub Kicinski wrote: > > > > > > On Thu, 22 Jan 2026 14:45:27 +0530 Srujana Challa wrote: > > > > Increase VIRTIO_NET_RSS_MAX_KEY_SIZE from 40 to 52 bytes to align= with > > > > the kernel's standard RSS key length defined by NETDEV_RSS_KEY_LE= N. > > > > > > I've been meaning to bump NETDEV_RSS_KEY_LEN to 128 or some such. > > > Most modern drivers can't use netdev_rss_key_fill() either because > > > core generates a tiny key. And the devices support hashing over two= > > > layers of IPv6 for tunnels. > > = > > Seems fine to me. Back in 2014, RSS was limited to 52 bytes on all kn= own NIC. > = > What is the purpose of extending? > = > The current length is sufficient for standard Toeplitz 4-tuple hashing.= Never mind, I should read better: > And the devices support hashing over two layers of IPv6 for tunnels. I'm hard pressed to see over 128 B of entropy. But if extending, might as well go to 256 B right away.