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([2001:288:7001:2703:751f:9418:61f4:229e]) by smtp.gmail.com with ESMTPSA id w6-20020a170902e88600b001e4ea358407sm15575142plg.46.2024.04.26.08.20.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Apr 2024 08:20:16 -0700 (PDT) From: I Hsin Cheng To: edumazet@google.com Cc: davem@davemloft.net, dsahern@kernel.org, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, I Hsin Cheng Subject: [PATCH] tcp_bbr: replace lambda expression with bitwise operation for bit flip Date: Fri, 26 Apr 2024 23:20:11 +0800 Message-Id: <20240426152011.37069-1-richard120310@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@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" In the origin implementation in function bbr_update_ack_aggregation(), we utilize a lambda expression to flip the bit value of bbr->extra_acked_win_idx. Since the data type of bbr->extra_acked_win_idx is simply a single bit, we are actually trying to perform a bit flip operation, under the fact we can simply perform a bitwise not operation on bbr->extra_acked_win_idx. This way we can elimate the need of possible branches which generate by the lambda function, they could result in branch misses sometimes. Perform a bitwise not operation is more straightforward and wouldn't generate branches. Signed-off-by: I Hsin Cheng --- net/ipv4/tcp_bbr.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c index 146792cd2..75068ba25 100644 --- a/net/ipv4/tcp_bbr.c +++ b/net/ipv4/tcp_bbr.c @@ -829,8 +829,7 @@ static void bbr_update_ack_aggregation(struct sock *sk, bbr->extra_acked_win_rtts + 1); if (bbr->extra_acked_win_rtts >=3D bbr_extra_acked_win_rtts) { bbr->extra_acked_win_rtts =3D 0; - bbr->extra_acked_win_idx =3D bbr->extra_acked_win_idx ? - 0 : 1; + bbr->extra_acked_win_idx =3D ~(bbr->extra_acked_win_idx); bbr->extra_acked[bbr->extra_acked_win_idx] =3D 0; } } --=20 2.34.1