From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f41.google.com (mail-ot1-f41.google.com [209.85.210.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2335B32470A for ; Wed, 1 Jul 2026 05:56:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.41 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782885379; cv=none; b=UPP+qvZjoYrsJXGseezuYvIiAgqnj0YInFhd81wa774jScyv69v2koaNNOYz89PTsztr9gcYpNlTXge9c0d/z5LIXjcNZ+S9DkJY2NBNsoh2BQ6iBWun6se/b6utD9uviEPfiB3tyCnDPxHOia8ZQrwB7aTl131EzH1hZ1/QzK4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782885379; c=relaxed/simple; bh=du69GUw1EIX5aANGYtoDtWVpbMocCveU908JccD8Dt8=; h=Mime-Version:Content-Type:Date:Message-Id:Subject:From:To: References:In-Reply-To; b=iUyRvDG23Q+5t+Z+k4UFx6DdWjVScNUXUFbRfwJMdddRwBWNYY50cPqkACH2fd2oxl8OB7g3zO/izD7o+ujiWAuyUHAfliw0ba5hLTBWZ7O/SHRpFymwIDuvT+B/7xksuZRjJSptUH38qprMUpXedK3rUaFOw13OliVYE0YFmU0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Xzx0XDdn; arc=none smtp.client-ip=209.85.210.41 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Xzx0XDdn" Received: by mail-ot1-f41.google.com with SMTP id 46e09a7af769-7e943356247so273166a34.2 for ; Tue, 30 Jun 2026 22:56:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1782885374; x=1783490174; darn=vger.kernel.org; h=in-reply-to:references:to:from:subject:message-id:date :content-transfer-encoding:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=PMHc6VjC8zpAtFBxLHo9uqSmcB6QkUimxcvK+ODJl3o=; b=Xzx0XDdnzBkey9K1juzhg7Occmgf7fcUA4KNpLpW/FRtUI1gHOIRWCZRKKY5aTLfp+ yTnon9oOc7eddpfQECZVqIKIiWi6M0hgBJyjaCcBcvqHFbDlZdx74RBGKJ16PhMpnpi3 3D8OZkuZlQPZRmbDbTufJ9ZsWtaX5kXl1meWq2aIXqN/7pwZZ8/FoPpxWBDQwnKH5FHe rixh0B26doerafmmBgfiT9sBnYTZPag5f7WoxzwzePOayo/tHRa0rJCP85D19QPmFClW EU1CpJgF3MNSVQFrwMgwY0R7dW0MIPUc1bg2Pynaki1tQH2PbAF4RmCURaMAo/MqqIZk YuRw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782885374; x=1783490174; h=in-reply-to:references:to:from:subject:message-id:date :content-transfer-encoding:mime-version:x-gm-gg:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=PMHc6VjC8zpAtFBxLHo9uqSmcB6QkUimxcvK+ODJl3o=; b=tJOBUe28GqF3rRm9nFr1GC0W0cb4IJ+w4Hpk9R9N7HmMBsB6qXotFlz0rM9rDbzrrj 4nkItfYUKj0cYoI9qOqnN8fQsvWIgON2vB8c4Zoty9zq6YqG9NrfrdGmE06ZOwO8Vnc+ iL/RU7C1H5aEj375EtDljtuj3e/4ImT5ZMQwC/1fpRgstK1f5t0WMTv+1MfrYQPjE97W YL6ADo47GlYz2iUlzLmDaenq6vqx+qhpO9SBQsIXUo97e4GAFWmI43uZkIzjVLkdni9z xDmtYfS8q7Nnd+hsVfTlhQ2sWWChL0uyN+eBR635ODAL8G/H3Nhu9MnLmAvUqmtg9HYB v7yg== X-Forwarded-Encrypted: i=1; AFNElJ/glvDcRVkTdLvTtHNk/NFb9ry2SyniyZQifhrL5ZOOXeALRf2P4usLRrmrWvYkVn2zics=@vger.kernel.org X-Gm-Message-State: AOJu0YzjeMHPXImR+VXBHDd2wt1CRDbaIhOBCiSNu5XfuYdXYeBdBi/+ JT9RidjljoTPQxg9SxaczDRsgwWev37ty+QR0TGarR0ACZ2Z2RMDO4pG X-Gm-Gg: AfdE7cnoG5kjROxoLPc/HSWJaNSOmwoycAvQKoP64vaPrgsnnwhtr13uFXAJ0L7jfkQ 8Clf8MkRr0aq3f/Y9HJ9GEE2A4+/k9UTNGq3+0lUYzkiYChfM5Zk/yyhPWjCiZdLbj9S67oI0rb qsHm0xGWUq0/wIUrC9OT0Wv29Hv+BmZYzWUsYs0pgGCWIcu6/x2dJ7AUT0DVTamWBnxpHpp/Rk4 cA7RVnZxySSxm5cqn0GZ4J99didhr/j4Z/8Nwsnxk60E/CmcpnF3483DIqIOQuTZlH5QkMH+UHP SfUENrHUgl+RY4Hoj4Gx3ZrfeXa4iAJ6iSj1jIvVdLx62+Tk1/xQEXJfBNtE5259o11E0D5HXX6 IPFj8KqcKor1Kv2aZHL7aS9XZ7Mxq8gdMKEIJmqa6sI8q+lq/f1qaRupxPsnThi6VgZu2WtdBh9 O+zb6BYvi8c2D7xyrVz8pANGEe+ETHdKaXIZ9QZGJzTMN6geMgnVqEl2WyDXKaFZBe5jNsyhud9 Mtffb0= X-Received: by 2002:a05:6830:81d2:b0:7e9:eaf2:edff with SMTP id 46e09a7af769-7eb4cc4cb36mr45738a34.26.1782885374015; Tue, 30 Jun 2026 22:56:14 -0700 (PDT) Received: from localhost ([2a03:2880:10ff:5f::]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7e9ec2e353fsm4114877a34.20.2026.06.30.22.56.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 30 Jun 2026 22:56:13 -0700 (PDT) Precedence: bulk X-Mailing-List: bpf@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.