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Tue, 30 Jun 2026 22:56:13 -0700 (PDT) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 30 Jun 2026 22:56:11 -0700 Message-Id: Subject: Re: [PATCH v3 net-next 1/1] tcp: Replace min_tso_segs() with tso_segs() CC callback From: "Alexei Starovoitov" To: "Chia-Yu Chang (Nokia)" , "jolsa@kernel.org" , "yonghong.song@linux.dev" , "song@kernel.org" , "linux-kselftest@vger.kernel.org" , "memxor@gmail.com" , "shuah@kernel.org" , "martin.lau@linux.dev" , "ast@kernel.org" , "daniel@iogearbox.net" , "andrii@kernel.org" , "eddyz87@gmail.com" , "horms@kernel.org" , "dsahern@kernel.org" , "bpf@vger.kernel.org" , "netdev@vger.kernel.org" , "pabeni@redhat.com" , "jhs@mojatatu.com" , "kuba@kernel.org" , "stephen@networkplumber.org" , "davem@davemloft.net" , "edumazet@google.com" , "andrew+netdev@lunn.ch" , "donald.hunter@gmail.com" , "kuniyu@google.com" , "ij@kernel.org" , "ncardwell@google.com" , "Koen De Schepper (Nokia)" , "g.white@cablelabs.com" , "ingemar.s.johansson@ericsson.com" , "mirja.kuehlewind@ericsson.com" , "cheshire@apple.com" , "rs.ietf@gmx.at" , "Jason_Livingood@comcast.com" , "vidhi_goel@apple.com" X-Mailer: aerc References: <20260630120145.286497-1-chia-yu.chang@nokia-bell-labs.com> In-Reply-To: On Tue Jun 30, 2026 at 10:46 PM PDT, Chia-Yu Chang (Nokia) wrote: >> > - /* override sysctl_tcp_min_tso_segs (optional) */ >> > - u32 (*min_tso_segs)(struct sock *sk); >> > + /* >> > + * Override tcp_tso_autosize (optional) >> > + * >> > + * If provided, this callback returns the final TSO segment numb= er >> > + * and will bypass tcp_tso_autosize() entirely. The implementati= on >> > + * must derive an appropriate value and ensure the result is val= id. >> > + */ >> > + u32 (*tso_segs)(struct sock *sk, u32 mss_now); >>=20 >> I don't like this interface change. >> It introduces churn for no good reason. >> At least I don't see why you cannot live with the existing api. > > Hi Alexei, > > This patch was part of TCP Prague preparation series: https://lore.kernel= .org/all/20260611161504.228319-4-chia-yu.chang@nokia-bell-labs.com/ > Our original patch is to add an extra tso_segs, and after discussion it's= recommended to replace exisiting min_tso_segs. > > This is needed because TCP Prague would set the exact TSO size rather tha= n using autosizing from TCP. > The TCP Prague itself is planned to be submitted after all preparation co= mmits are accepted. > You can find its current stauts: https://github.com/L4STeam/linux-net-nex= t/blob/upstream_l4steam/net/ipv4/tcp_prague.c You have to explain why Prague CC cannot rely on autosizing. To me it sounds like a red flag. autosizing logic was there for a decade, i= f not more. And now you're arguing that your CC logic is special and it deserves new AP= I and breakage of existing convention. Maybe you should step back and reconsider.