From: "Toke Høiland-Jørgensen" <toke@toke•dk>
To: Eric Dumazet <edumazet@google•com>,
"David S . Miller" <davem@davemloft•net>
Cc: netdev <netdev@vger•kernel.org>,
Neal Cardwell <ncardwell@google•com>,
Yuchung Cheng <ycheng@google•com>,
Soheil Hassas Yeganeh <soheil@google•com>,
Eric Dumazet <edumazet@google•com>,
Eric Dumazet <eric.dumazet@gmail•com>
Subject: Re: [PATCH v3 net-next 3/6] tcp: add SACK compression
Date: Fri, 18 May 2018 01:24:07 +0200 [thread overview]
Message-ID: <87o9hd6f3c.fsf@toke.dk> (raw)
In-Reply-To: <20180517214729.186094-4-edumazet@google.com>
Eric Dumazet <edumazet@google•com> writes:
> When TCP receives an out-of-order packet, it immediately sends
> a SACK packet, generating network load but also forcing the
> receiver to send 1-MSS pathological packets, increasing its
> RTX queue length/depth, and thus processing time.
>
> Wifi networks suffer from this aggressive behavior, but generally
> speaking, all these SACK packets add fuel to the fire when networks
> are under congestion.
>
> This patch adds a high resolution timer and tp->compressed_ack counter.
>
> Instead of sending a SACK, we program this timer with a small delay,
> based on RTT and capped to 1 ms :
>
> delay = min ( 5 % of RTT, 1 ms)
>
> If subsequent SACKs need to be sent while the timer has not yet
> expired, we simply increment tp->compressed_ack.
>
> When timer expires, a SACK is sent with the latest information.
> Whenever an ACK is sent (if data is sent, or if in-order
> data is received) timer is canceled.
>
> Note that tcp_sack_new_ofo_skb() is able to force a SACK to be sent
> if the sack blocks need to be shuffled, even if the timer has not
> expired.
>
> A new SNMP counter is added in the following patch.
>
> Two other patches add sysctls to allow changing the 1,000,000 and 44
> values that this commit hard-coded.
>
> Signed-off-by: Eric Dumazet <edumazet@google•com>
Acked-by: Toke Høiland-Jørgensen <toke@toke•dk>
next prev parent reply other threads:[~2018-05-17 23:24 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-17 21:47 [PATCH v3 net-next 0/6] tcp: implement SACK compression Eric Dumazet
2018-05-17 21:47 ` [PATCH v3 net-next 1/6] tcp: use __sock_put() instead of sock_put() in tcp_clear_xmit_timers() Eric Dumazet
2018-05-17 21:47 ` [PATCH v3 net-next 2/6] tcp: do not force quickack when receiving out-of-order packets Eric Dumazet
2018-05-17 21:47 ` [PATCH v3 net-next 3/6] tcp: add SACK compression Eric Dumazet
2018-05-17 21:57 ` Neal Cardwell
2018-05-17 22:14 ` Yuchung Cheng
2018-05-17 23:24 ` Toke Høiland-Jørgensen [this message]
2018-05-17 21:47 ` [PATCH v3 net-next 4/6] tcp: add TCPAckCompressed SNMP counter Eric Dumazet
2018-05-17 21:47 ` [PATCH v3 net-next 5/6] tcp: add tcp_comp_sack_delay_ns sysctl Eric Dumazet
2018-05-17 21:59 ` Neal Cardwell
2018-05-17 21:47 ` [PATCH v3 net-next 6/6] tcp: add tcp_comp_sack_nr sysctl Eric Dumazet
2018-05-17 22:01 ` Neal Cardwell
2018-05-18 15:42 ` [PATCH v3 net-next 0/6] tcp: implement SACK compression David Miller
2018-05-18 15:48 ` Eric Dumazet
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