From: I Hsin Cheng <richard120310@gmail.com>
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 <richard120310@gmail.com>
Subject: [PATCH] tcp_bbr: replace lambda expression with bitwise operation for bit flip
Date: Fri, 26 Apr 2024 23:20:11 +0800 [thread overview]
Message-ID: <20240426152011.37069-1-richard120310@gmail.com> (raw)
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 <richard120310@gmail.com>
---
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 >= bbr_extra_acked_win_rtts) {
bbr->extra_acked_win_rtts = 0;
- bbr->extra_acked_win_idx = bbr->extra_acked_win_idx ?
- 0 : 1;
+ bbr->extra_acked_win_idx = ~(bbr->extra_acked_win_idx);
bbr->extra_acked[bbr->extra_acked_win_idx] = 0;
}
}
--
2.34.1
next reply other threads:[~2024-04-26 15:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-26 15:20 I Hsin Cheng [this message]
2024-04-26 15:32 ` [PATCH] tcp_bbr: replace lambda expression with bitwise operation for bit flip Eric Dumazet
2024-04-26 17:01 ` I Hsin Cheng
2024-04-26 20:19 ` Al Viro
2024-04-27 8:31 ` I Hsin Cheng
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