From: Eric Dumazet <eric.dumazet@gmail.com>
To: Lawrence Brakmo <brakmo@fb.com>, netdev <netdev@vger.kernel.org>
Cc: Kernel Team <kernel-team@fb.com>, Blake Matheny <bmatheny@fb.com>,
Alexei Starovoitov <ast@fb.com>
Subject: Re: [PATCH net-next v2] tcp: force cwnd at least 2 in tcp_cwnd_reduction
Date: Wed, 27 Jun 2018 08:04:57 -0700 [thread overview]
Message-ID: <d07bfdf1-2060-bdaf-8df0-7e33a8f017b7@gmail.com> (raw)
In-Reply-To: <20180627023403.3395818-1-brakmo@fb.com>
On 06/26/2018 07:34 PM, Lawrence Brakmo wrote:
> When using dctcp and doing RPCs, if the last packet of a request is
> ECN marked as having seen congestion (CE), the sender can decrease its
> cwnd to 1. As a result, it will only send one packet when a new request
> is sent. In some instances this results in high tail latencies.
>
> }
> /* Force a fast retransmit upon entering fast recovery */
> sndcnt = max(sndcnt, (tp->prr_out ? 0 : 1));
> - tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt;
> + tp->snd_cwnd = max((int)tcp_packets_in_flight(tp) + sndcnt, 2);
Canonical way is to use min_t(), please respin (no need to explain this trivia in changelog)
Thanks.
next prev parent reply other threads:[~2018-06-27 15:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-27 2:34 [PATCH net-next v2] tcp: force cwnd at least 2 in tcp_cwnd_reduction Lawrence Brakmo
2018-06-27 15:04 ` Eric Dumazet [this message]
2018-06-27 15:06 ` Eric Dumazet
2018-06-27 15:24 ` Neal Cardwell
2018-06-27 16:57 ` Yuchung Cheng
[not found] ` <9745C5DD-BB86-4A7D-B607-4B8AA0E07245@fb.com>
2018-06-27 22:27 ` Yuchung Cheng
[not found] ` <ADD5DEDF-213D-4375-B556-E9E44DD94130@fb.com>
2018-06-28 20:47 ` Neal Cardwell
2018-06-28 20:58 ` Lawrence Brakmo
2018-06-29 4:32 ` Lawrence Brakmo
2018-06-29 18:55 ` Lawrence Brakmo
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