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([2a0d:3344:2712:7e10:4d59:d956:544f:d65c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-464f64ad30csm271970905e9.23.2025.09.23.02.32.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Sep 2025 02:32:49 -0700 (PDT) Message-ID: Date: Tue, 23 Sep 2025 11:32:47 +0200 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 net-next 01/14] tcp: try to avoid safer when ACKs are thinned To: chia-yu.chang@nokia-bell-labs.com, edumazet@google.com, linux-doc@vger.kernel.org, corbet@lwn.net, horms@kernel.org, dsahern@kernel.org, kuniyu@amazon.com, bpf@vger.kernel.org, netdev@vger.kernel.org, dave.taht@gmail.com, jhs@mojatatu.com, kuba@kernel.org, stephen@networkplumber.org, xiyou.wangcong@gmail.com, jiri@resnulli.us, davem@davemloft.net, andrew+netdev@lunn.ch, donald.hunter@gmail.com, ast@fiberby.net, liuhangbin@gmail.com, shuah@kernel.org, linux-kselftest@vger.kernel.org, ij@kernel.org, ncardwell@google.com, koen.de_schepper@nokia-bell-labs.com, 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 References: <20250918162133.111922-1-chia-yu.chang@nokia-bell-labs.com> <20250918162133.111922-2-chia-yu.chang@nokia-bell-labs.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20250918162133.111922-2-chia-yu.chang@nokia-bell-labs.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/18/25 6:21 PM, chia-yu.chang@nokia-bell-labs.com wrote: > diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c > index 9fdc6ce25eb1..0b25bf03ae6a 100644 > --- a/net/ipv4/tcp_input.c > +++ b/net/ipv4/tcp_input.c > @@ -488,6 +488,10 @@ static void tcp_count_delivered(struct tcp_sock *tp, u32 delivered, > tcp_count_delivered_ce(tp, delivered); > } > > +#define PKTS_ACKED_WEIGHT 6 > +#define PKTS_ACKED_PREC 6 > +#define ACK_COMP_THRESH 4 > + > /* Returns the ECN CE delta */ > static u32 __tcp_accecn_process(struct sock *sk, const struct sk_buff *skb, > u32 delivered_pkts, u32 delivered_bytes, > @@ -507,6 +511,19 @@ static u32 __tcp_accecn_process(struct sock *sk, const struct sk_buff *skb, > opt_deltas_valid = tcp_accecn_process_option(tp, skb, > delivered_bytes, flag); > > + if (delivered_pkts) { > + if (!tp->pkts_acked_ewma) { > + tp->pkts_acked_ewma = delivered_pkts << PKTS_ACKED_PREC; Can the above statement overflow pkts_acked_ewma in exceptional cases? Do that need and additional min_t(u32, , 0xFFFFU)? /P