From: Neal Cardwell <ncardwell@google.com>
To: Pengcheng Yang <yangpc@wangsu.com>
Cc: Eric Dumazet <edumazet@google.com>,
David Miller <davem@davemloft.net>,
Netdev <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RESEND net-next v2 2/5] tcp: fix stretch ACK bugs in Scalable
Date: Mon, 16 Mar 2020 17:25:41 -0400 [thread overview]
Message-ID: <CADVnQy=nhaKY8Ub84TvFH4cFtW92_TU72OxXnV32FzdEGtDCvw@mail.gmail.com> (raw)
In-Reply-To: <1584340511-9870-3-git-send-email-yangpc@wangsu.com>
On Mon, Mar 16, 2020 at 2:37 AM Pengcheng Yang <yangpc@wangsu.com> wrote:
>
> Change Scalable to properly handle stretch ACKs in additive
> increase mode by passing in the count of ACKed packets to
> tcp_cong_avoid_ai().
>
> In addition, because we are now precisely accounting for
> stretch ACKs, including delayed ACKs, we can now change
> TCP_SCALABLE_AI_CNT to 100.
>
> Signed-off-by: Pengcheng Yang <yangpc@wangsu.com>
> ---
> net/ipv4/tcp_scalable.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/net/ipv4/tcp_scalable.c b/net/ipv4/tcp_scalable.c
> index 471571e..6cebf41 100644
> --- a/net/ipv4/tcp_scalable.c
> +++ b/net/ipv4/tcp_scalable.c
> @@ -10,10 +10,9 @@
> #include <net/tcp.h>
>
> /* These factors derived from the recommended values in the aer:
> - * .01 and and 7/8. We use 50 instead of 100 to account for
> - * delayed ack.
> + * .01 and and 7/8.
> */
> -#define TCP_SCALABLE_AI_CNT 50U
> +#define TCP_SCALABLE_AI_CNT 100U
> #define TCP_SCALABLE_MD_SCALE 3
>
> static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
> @@ -23,11 +22,13 @@ static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
> if (!tcp_is_cwnd_limited(sk))
> return;
>
> - if (tcp_in_slow_start(tp))
> - tcp_slow_start(tp, acked);
> - else
> - tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
> - 1);
> + if (tcp_in_slow_start(tp)) {
> + acked = tcp_slow_start(tp, acked);
> + if (!acked)
> + return;
> + }
> + tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
> + acked);
> }
>
> static u32 tcp_scalable_ssthresh(struct sock *sk)
> --
Acked-by: Neal Cardwell <ncardwell@google.com>
thanks,
neal
next prev parent reply other threads:[~2020-03-16 21:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-16 6:35 [PATCH RESEND net-next v2 0/5] tcp: fix stretch ACK bugs in congestion control modules Pengcheng Yang
2020-03-16 6:35 ` [PATCH RESEND net-next v2 1/5] tcp: fix stretch ACK bugs in BIC Pengcheng Yang
2020-03-16 21:19 ` Neal Cardwell
2020-03-16 6:35 ` [PATCH RESEND net-next v2 2/5] tcp: fix stretch ACK bugs in Scalable Pengcheng Yang
2020-03-16 21:25 ` Neal Cardwell [this message]
2020-03-16 6:35 ` [PATCH RESEND net-next v2 3/5] tcp: stretch ACK fixes in Veno prep Pengcheng Yang
2020-03-16 21:42 ` Neal Cardwell
2020-03-16 6:35 ` [PATCH RESEND net-next v2 4/5] tcp: fix stretch ACK bugs in Veno Pengcheng Yang
2020-03-16 21:46 ` Neal Cardwell
2020-03-16 6:35 ` [PATCH RESEND net-next v2 5/5] tcp: fix stretch ACK bugs in Yeah Pengcheng Yang
2020-03-17 1:27 ` [PATCH RESEND net-next v2 0/5] tcp: fix stretch ACK bugs in congestion control modules David Miller
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