diff options
| author | Eric Dumazet <edumazet@google.com> | 2018-05-18 00:47:26 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-05-18 18:40:27 +0300 |
| commit | 5d9f4262b7ea41ca9981cc790e37cca6e37c789e (patch) | |
| tree | cae663c7a66f7a37aeb26d1587012b9d91fb1a2c /include | |
| parent | a3893637e1eb0ef5eb1bbc52b3a8d2dfa317a35d (diff) | |
| download | linux-5d9f4262b7ea41ca9981cc790e37cca6e37c789e.tar.xz | |
tcp: add SACK compression
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: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/tcp.h | 2 | ||||
| -rw-r--r-- | include/net/tcp.h | 3 |
2 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 807776928cb8..72705eaf4b84 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -218,6 +218,7 @@ struct tcp_sock { reord:1; /* reordering detected */ } rack; u16 advmss; /* Advertised MSS */ + u8 compressed_ack; u32 chrono_start; /* Start time in jiffies of a TCP chrono */ u32 chrono_stat[3]; /* Time in jiffies for chrono_stat stats */ u8 chrono_type:2, /* current chronograph type */ @@ -297,6 +298,7 @@ struct tcp_sock { u32 sacked_out; /* SACK'd packets */ struct hrtimer pacing_timer; + struct hrtimer compressed_ack_timer; /* from STCP, retrans queue hinting */ struct sk_buff* lost_skb_hint; diff --git a/include/net/tcp.h b/include/net/tcp.h index 511bd0fde1dc..952d842a604a 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -561,6 +561,9 @@ static inline void tcp_clear_xmit_timers(struct sock *sk) if (hrtimer_try_to_cancel(&tcp_sk(sk)->pacing_timer) == 1) __sock_put(sk); + if (hrtimer_try_to_cancel(&tcp_sk(sk)->compressed_ack_timer) == 1) + __sock_put(sk); + inet_csk_clear_xmit_timers(sk); } |