Commit 737ff314 authored by Yuchung Cheng's avatar Yuchung Cheng Committed by David S. Miller

tcp: use sequence distance to detect reordering

Replace the reordering distance measurement in packet unit with
sequence based approach. Previously it trackes the number of "packets"
toward the forward ACK (i.e.  highest sacked sequence)in a state
variable "fackets_out".

Precisely measuring reordering degree on packet distance has not much
benefit, as the degree constantly changes by factors like path, load,
and congestion window. It is also complicated and prone to arcane bugs.
This patch replaces with sequence-based approach that's much simpler.
Signed-off-by: 's avatarYuchung Cheng <ycheng@google.com>
Reviewed-by: 's avatarEric Dumazet <edumazet@google.com>
Reviewed-by: 's avatarNeal Cardwell <ncardwell@google.com>
Reviewed-by: 's avatarSoheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: 's avatarPriyaranjan Jha <priyarjha@google.com>
Signed-off-by: 's avatarDavid S. Miller <davem@davemloft.net>
parent 713bafea
......@@ -293,7 +293,6 @@ struct tcp_sock {
u32 pushed_seq; /* Last pushed seq, required to talk to windows */
u32 lost_out; /* Lost packets */
u32 sacked_out; /* SACK'd packets */
u32 fackets_out; /* FACK'd packets */
struct hrtimer pacing_timer;
......
......@@ -2977,7 +2977,6 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info)
info->tcpi_lost = tp->lost_out;
info->tcpi_retrans = tp->retrans_out;
info->tcpi_fackets = tp->fackets_out;
now = tcp_jiffies32;
info->tcpi_last_data_sent = jiffies_to_msecs(now - tp->lsndtime);
......
This diff is collapsed.
......@@ -475,7 +475,6 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
newtp->packets_out = 0;
newtp->retrans_out = 0;
newtp->sacked_out = 0;
newtp->fackets_out = 0;
newtp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
newtp->tlp_high_seq = 0;
newtp->lsndtime = tcp_jiffies32;
......
......@@ -1218,21 +1218,6 @@ static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
}
}
/* When a modification to fackets out becomes necessary, we need to check
* skb is counted to fackets_out or not.
*/
static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
int decr)
{
struct tcp_sock *tp = tcp_sk(sk);
if (!tp->sacked_out || tcp_is_reno(tp))
return;
if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
tp->fackets_out -= decr;
}
/* Pcount in the middle of the write queue got changed, we need to do various
* tweaks to fix counters
*/
......@@ -1253,8 +1238,6 @@ static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int de
if (tcp_is_reno(tp) && decr > 0)
tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
tcp_adjust_fackets_out(sk, skb, decr);
if (tp->lost_skb_hint &&
before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
......
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