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Tue, 22 Jul 2025 21:34:36 -0700 (PDT) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250721031609.132217-1-krikku@gmail.com> <20250721031609.132217-2-krikku@gmail.com> In-Reply-To: From: Krishna Kumar Date: Wed, 23 Jul 2025 10:03:59 +0530 X-Gm-Features: Ac12FXzkTUn1EM4ku_x0eMNpTpooec26y7ZSMo2akQqm-V7Mvxe56oijtutxKGg Message-ID: Subject: Re: [PATCH v5 net-next 1/2] net: Prevent RPS table overwrite for active flows To: Eric Dumazet Cc: netdev@vger.kernel.org, davem@davemloft.net, tom@herbertland.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, sdf@fomichev.me, kuniyu@google.com, ahmed.zaki@intel.com, aleksander.lobakin@intel.com, atenart@kernel.org, krishna.ku@flipkart.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Eric, On Mon, Jul 21, 2025 at 1:44=E2=80=AFPM Eric Dumazet = wrote: > > struct rps_dev_flow { > > u16 cpu; > > u16 filter; > > unsigned int last_qtail; > > + u32 hash; > > This is problematic, because adds an extra potential cache line miss in R= PS. > > Some of us do not use CONFIG_RFS_ACCEL, make sure to not add extra > costs for this configuration ? I will send this fix today. On your point on making the active check less obscure/costly, my understanding is we need last_qtail for in-order processing and add something like last_use for activity detection. If that=E2=80=99s correct, I can send a patch for it after this. Thanks, - Krishna