diff options
| -rw-r--r-- | include/linux/tcp.h | 1 | ||||
| -rw-r--r-- | include/net/tcp.h | 22 | ||||
| -rw-r--r-- | net/ipv4/tcp_cong.c | 20 | ||||
| -rw-r--r-- | net/ipv4/tcp_output.c | 21 |
4 files changed, 36 insertions, 28 deletions
diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 239946868142..4e37c71ecd74 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -230,6 +230,7 @@ struct tcp_sock { u32 snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */ u32 snd_cwnd_used; u32 snd_cwnd_stamp; + u32 lsnd_pending; /* packets inflight or unsent since last xmit */ u32 prior_cwnd; /* Congestion window at start of Recovery. */ u32 prr_delivered; /* Number of newly delivered packets to * receiver in Recovery. */ diff --git a/include/net/tcp.h b/include/net/tcp.h index 163d2b467d78..a9fe7bc4f4bb 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -974,7 +974,27 @@ static inline u32 tcp_wnd_end(const struct tcp_sock *tp) { return tp->snd_una + tp->snd_wnd; } -bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight); + +/* We follow the spirit of RFC2861 to validate cwnd but implement a more + * flexible approach. The RFC suggests cwnd should not be raised unless + * it was fully used previously. But we allow cwnd to grow as long as the + * application has used half the cwnd. + * Example : + * cwnd is 10 (IW10), but application sends 9 frames. + * We allow cwnd to reach 18 when all frames are ACKed. + * This check is safe because it's as aggressive as slow start which already + * risks 100% overshoot. The advantage is that we discourage application to + * either send more filler packets or data to artificially blow up the cwnd + * usage, and allow application-limited process to probe bw more aggressively. + * + * TODO: remove in_flight once we can fix all callers, and their callers... + */ +static inline bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight) +{ + const struct tcp_sock *tp = tcp_sk(sk); + + return tp->snd_cwnd < 2 * tp->lsnd_pending; +} static inline void tcp_check_probe_timer(struct sock *sk) { diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index 2b9464c93b88..a93b41ba05ff 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -276,26 +276,6 @@ int tcp_set_congestion_control(struct sock *sk, const char *name) return err; } -/* RFC2861 Check whether we are limited by application or congestion window - * This is the inverse of cwnd check in tcp_tso_should_defer - */ -bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight) -{ - const struct tcp_sock *tp = tcp_sk(sk); - u32 left; - - if (in_flight >= tp->snd_cwnd) - return true; - - left = tp->snd_cwnd - in_flight; - if (sk_can_gso(sk) && - left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd && - left < tp->xmit_size_goal_segs) - return true; - return left <= tcp_max_tso_deferred_mss(tp); -} -EXPORT_SYMBOL_GPL(tcp_is_cwnd_limited); - /* Slow start is used when congestion window is no greater than the slow start * threshold. We base on RFC2581 and also handle stretch ACKs properly. * We do not implement RFC3465 Appropriate Byte Counting (ABC) per se but diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 20847de991ea..f9181a133462 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1402,12 +1402,13 @@ static void tcp_cwnd_application_limited(struct sock *sk) tp->snd_cwnd_stamp = tcp_time_stamp; } -/* Congestion window validation. (RFC2861) */ -static void tcp_cwnd_validate(struct sock *sk) +static void tcp_cwnd_validate(struct sock *sk, u32 unsent_segs) { struct tcp_sock *tp = tcp_sk(sk); - if (tp->packets_out >= tp->snd_cwnd) { + tp->lsnd_pending = tp->packets_out + unsent_segs; + + if (tcp_is_cwnd_limited(sk, 0)) { /* Network is feed fully. */ tp->snd_cwnd_used = 0; tp->snd_cwnd_stamp = tcp_time_stamp; @@ -1880,7 +1881,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, { struct tcp_sock *tp = tcp_sk(sk); struct sk_buff *skb; - unsigned int tso_segs, sent_pkts; + unsigned int tso_segs, sent_pkts, unsent_segs = 0; int cwnd_quota; int result; @@ -1924,7 +1925,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, break; } else { if (!push_one && tcp_tso_should_defer(sk, skb)) - break; + goto compute_unsent_segs; } /* TCP Small Queues : @@ -1949,8 +1950,14 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, * there is no smp_mb__after_set_bit() yet */ smp_mb__after_clear_bit(); - if (atomic_read(&sk->sk_wmem_alloc) > limit) + if (atomic_read(&sk->sk_wmem_alloc) > limit) { + u32 unsent_bytes; + +compute_unsent_segs: + unsent_bytes = tp->write_seq - tp->snd_nxt; + unsent_segs = DIV_ROUND_UP(unsent_bytes, mss_now); break; + } } limit = mss_now; @@ -1990,7 +1997,7 @@ repair: /* Send one loss probe per tail loss episode. */ if (push_one != 2) tcp_schedule_loss_probe(sk); - tcp_cwnd_validate(sk); + tcp_cwnd_validate(sk, unsent_segs); return false; } return (push_one == 2) || (!tp->packets_out && tcp_send_head(sk)); |