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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c249685ef7bsm1665564366b.52.2026.08.24.13.26.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Aug 2026 13:26:21 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kselftest@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: Mon, 24 Aug 2026 22:26:19 +0200 Message-Id: Cc: "john.fastabend@gmail.com" , "jakub@cloudflare.com" , "jiayuan.chen@linux.dev" , "netdev@vger.kernel.org" , "bpf@vger.kernel.org" , "ast@kernel.org" , "daniel@iogearbox.net" , "andrii@kernel.org" , "eddyz87@gmail.com" , "martin.lau@linux.dev" , "song@kernel.org" , "yonghong.song@linux.dev" , "jolsa@kernel.org" , "emil@etsalapatis.com" , "linux-kselftest@vger.kernel.org" , "shuah@kernel.org" , "horms@kernel.org" , "dsahern@kernel.org" , "pabeni@redhat.com" , "jhs@mojatatu.com" , "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" , "Mike_Rudolph@comcast.com" , "Jeff_Howe@comcast.com" , "srichard@netapp.com" Subject: Re: [PATCH v8 net-next 0/2] Explicit TSO segment count From: "Kumar Kartikeya Dwivedi" To: "Chia-Yu Chang (Nokia)" , "Jakub Kicinski" X-Mailer: aerc 0.21.0 References: <20260824163139.990734-1-chia-yu.chang@nokia-bell-labs.com> <20260824130511.2955f30d@kernel.org> In-Reply-To: On Mon Aug 24, 2026 at 10:21 PM CEST, Chia-Yu Chang (Nokia) wrote: >> -----Original Message----- >> From: Kumar Kartikeya Dwivedi >> Sent: Monday, August 24, 2026 10:10 PM >> To: Jakub Kicinski ; Chia-Yu Chang (Nokia) >> Cc: john.fastabend@gmail.com; jakub@cloudflare.com; jiayuan.chen@linux.d= ev; netdev@vger.kernel.org; bpf@vger.kernel.org; ast@kernel.org; daniel@iog= earbox.net; andrii@kernel.org; eddyz87@gmail.com; martin.lau@linux.dev; son= g@kernel.org; yonghong.song@linux.dev; jolsa@kernel.org; emil@etsalapatis.c= om; linux-kselftest@vger.kernel.org; shuah@kernel.org; horms@kernel.org; ds= ahern@kernel.org; pabeni@redhat.com; jhs@mojatatu.com; stephen@networkplumb= er.org; davem@davemloft.net; edumazet@google.com; andrew+netdev@lunn.ch; do= nald.hunter@gmail.com; kuniyu@google.com; ij@kernel.org; ncardwell@google.c= om; Koen De Schepper (Nokia) ; g.whit= e@cablelabs.com; ingemar.s.johansson@ericsson.com; mirja.kuehlewind@ericsso= n.com; cheshire@apple.com; rs.ietf@gmx.at; Jason_Livingood@comcast.com; vid= hi_goel@apple.com; Mike_Rudolph@comcast.com; Jeff_Howe@comcast.com; srichar= d@netapp.com >> Subject: Re: [PATCH v8 net-next 0/2] Explicit TSO segment count >> >> >> CAUTION: This is an external email. Please be very careful when clicking= links or opening attachments. See the URL nok.it/ext for additional inform= ation. >> >> >> >> On Mon Aug 24, 2026 at 10:05 PM CEST, Jakub Kicinski wrote: >> > On Mon, 24 Aug 2026 18:31:37 +0200 chia-yu.chang@nokia-bell-labs.com >> > wrote: >> >> From: Chia-Yu Chang >> >> >> >> Hello, >> >> >> >> This series replaces the existing min_tso_segs() congestion control >> >> callback with a new tso_segs() callback that allows congestion >> >> control algorithms to provide an explicit TSO segment count for each = data burst. >> >> >> >> To support BPF congestion controls, the series also exposes >> >> tcp_tso_autosize() as a BPF kfunc, allowing BPF implementations to >> >> reuse the kernel TSO autosizing logic while implementing custom >> >> tso_segs() callbacks. >> > >> > AI CI says: >> > >> > The bpf-ci build jobs are failing for this patch on all tested >> > architectures/toolchains (x86-64 gcc-15, x86-64 llvm-21, aarch64 >> > gcc-15, s390x gcc-15), all with the same link-time error: >> > >> > net/ipv4/tcp_bbr.o: in function `__BTF_ID__set8__tcp_bbr_check_kfunc= _ids': >> > tcp_bbr.c:(.BTF_ids+0x...): undefined reference to `KF_DEPRECATED' >> > >> > This comes from the change to net/ipv4/tcp_bbr.c that marks the >> > retained >> > bbr_min_tso_segs() kfunc entry with the KF_DEPRECATED flag: >> > >> > BTF_ID_FLAGS(func, bbr_min_tso_segs, KF_DEPRECATED) >> > BTF_ID_FLAGS(func, bbr_tso_segs) >> > >> > KF_DEPRECATED does not resolve to a usable symbol/flag in this tree, >> > so the BTF id set for tcp_bbr fails to link into vmlinux on every >> > architecture and toolchain -- it's a straight undefined-reference >> > error, not a per-arch/per-config issue. >> > >> > Could you drop the KF_DEPRECATED flag (or use a flag that this kfunc >> > infrastructure actually defines) on bbr_min_tso_segs, and re-verify >> > that the kernel links cleanly? A local `make net/ipv4/tcp_bbr.o >> > vmlinux` build (or the bpf-ci selftest build job) should reproduce thi= s quickly. >> > >> > Full build log for reference: >> > >> > ld.lld-21: error: undefined symbol: KF_DEPRECATED >> > >>> referenced by usercopy_64.c >> > >>> vmlinux.o:(__BTF_ID__set8__tcp_bbr_check_kfunc_ids= ) >> >> I think Chia-Yu's AI is hallucinating, it was a proposed flag but not ad= ded yet... > > Hi Kumar and Kuba, > > I will drop it in the next version; however, this AI hallucination is fro= m Sashiko's feedback I got: > > https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260814173034.749151= -1-chia-yu.chang%40nokia-bell-labs.com > > BTW, any BPF-related flag is suggested to be added for graceful degradati= on? > We don't have anything yet, but I will add something this cycle and figure = out how this can be marked deprecated then. > Thanks. > Chia-Yu