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AJvYcCW9zzkSQiF4BVq9MGb7y8sJKBdMndK5r8574s945MI5WkHfYgqNbsLRmUHWOPYiu4Ucfg8pR6M=@vger.kernel.org X-Gm-Message-State: AOJu0YwkHjTwLDJMmcy5TiAJTuSibtSJJNpnpISfLF1wHAKPMpfD8loc u0GVuNxoxNX2PbcXN5QsHhZcpKlEBxba2+BRC/9Npj7NHXxD67U/ X-Google-Smtp-Source: AGHT+IE5NdfDauglm2+uBOlPYEKxcKEpKcZvsV3utkV0/On4GK7OVxmR3q8XjtkIXw/33H2UOk+1OA== X-Received: by 2002:a05:6602:15d3:b0:7fa:a253:a1cc with SMTP id ca18e2360f4ac-824f263255fmr1482192039f.3.1724101401202; Mon, 19 Aug 2024 14:03:21 -0700 (PDT) Received: from [10.64.61.212] ([129.93.161.236]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-4ccd6f3e3f2sm3336973173.100.2024.08.19.14.03.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 Aug 2024 14:03:20 -0700 (PDT) Message-ID: Date: Mon, 19 Aug 2024 16:03:20 -0500 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v4 2/3] tcp_cubic: fix to match Reno additive increment To: Eric Dumazet Cc: davem@davemloft.net, ncardwell@google.com, netdev@vger.kernel.org, Lisong Xu References: <20240817163400.2616134-1-mrzhang97@gmail.com> <20240817163400.2616134-3-mrzhang97@gmail.com> Content-Language: en-US From: Mingrui Zhang In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 8/19/24 03:22, Eric Dumazet wrote: > On Sat, Aug 17, 2024 at 6:35 PM Mingrui Zhang wrote: >> The original code follows RFC 8312 (obsoleted CUBIC RFC). >> >> The patched code follows RFC 9438 (new CUBIC RFC): > Please give the precise location in the RFC (4.3 Reno-Friendly Region) Thank you, Eric, I will write it more clearly in the next version patch to submit. > >> "Once _W_est_ has grown to reach the _cwnd_ at the time of most >> recently setting _ssthresh_ -- that is, _W_est_ >= _cwnd_prior_ -- >> the sender SHOULD set α__cubic_ to 1 to ensure that it can achieve >> the same congestion window increment rate as Reno, which uses AIMD >> (1,0.5)." >> >> Add new field 'cwnd_prior' in bictcp to hold cwnd before a loss event >> >> Fixes: 89b3d9aaf467 ("[TCP] cubic: precompute constants") > RFC 9438 is brand new, I think we should not backport this patch to > stable linux versions. > > This would target net-next, unless there is clear evidence that it is > absolutely safe. I agree with you that this patch would target net-next. > Note the existence of tools/testing/selftests/bpf/progs/bpf_cc_cubic.c > and tools/testing/selftests/bpf/progs/bpf_cubic.c > > If this patch was a fix, I presume we would need to fix these files ? In my understanding, the bpf_cubic.c and bpf_cc_cubic.c are not designed to create a fully equivalent version of tcp_cubic, but more focus on BPF logic testing usage. For example, the up-to-date bpf_cubic does not involve the changes in commit 9957b38b5e7a ("tcp_cubic: make hystart_ack_delay() aware of BIG TCP") Maybe we would ask BPF maintainers whether to fix these BPF files?