[PATCH net-next] tcp: tracking packets with CE marks in BW rate sample
From: Luke Hsiao <hidden>
Date: 2021-09-23 21:17:54
From: Yuchung Cheng <redacted> In order to track CE marks per rate sample (one round trip), TCP needs a per-skb header field to record the tp->delivered_ce count when the skb was sent. To make space, we replace the "last_in_flight" field which is used exclusively for NV congestion control. The stat needed by NV can be alternatively approximated by existing stats tcp_sock delivered and mss_cache. This patch counts the number of packets delivered which have CE marks in the rate sample, using similar approach of delivery accounting. Cc: Lawrence Brakmo <redacted> Signed-off-by: Yuchung Cheng <redacted> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Luke Hsiao <redacted> --- include/net/tcp.h | 9 ++++++--- net/ipv4/tcp_input.c | 11 +++++------ net/ipv4/tcp_output.c | 2 -- net/ipv4/tcp_rate.c | 6 ++++++ 4 files changed, 17 insertions(+), 11 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 673c3b01e287..32cf6c01f403 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h@@ -874,10 +874,11 @@ struct tcp_skb_cb { __u32 ack_seq; /* Sequence number ACK'd */ union { struct { +#define TCPCB_DELIVERED_CE_MASK ((1U<<20) - 1) /* There is space for up to 24 bytes */ - __u32 in_flight:30,/* Bytes in flight at transmit */ - is_app_limited:1, /* cwnd not fully used? */ - unused:1; + __u32 is_app_limited:1, /* cwnd not fully used? */ + delivered_ce:20, + unused:11; /* pkts S/ACKed so far upon tx of skb, incl retrans: */ __u32 delivered; /* start of send pipeline phase */
@@ -1029,7 +1030,9 @@ struct ack_sample { struct rate_sample { u64 prior_mstamp; /* starting timestamp for interval */ u32 prior_delivered; /* tp->delivered at "prior_mstamp" */ + u32 prior_delivered_ce;/* tp->delivered_ce at "prior_mstamp" */ s32 delivered; /* number of packets delivered over interval */ + s32 delivered_ce; /* number of packets delivered w/ CE marks*/ long interval_us; /* time for tp->delivered to incr "delivered" */ u32 snd_interval_us; /* snd interval for delivered packets */ u32 rcv_interval_us; /* rcv interval for delivered packets */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 141e85e6422b..53675e284841 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c@@ -3221,7 +3221,6 @@ static int tcp_clean_rtx_queue(struct sock *sk, const struct sk_buff *ack_skb, long seq_rtt_us = -1L; long ca_rtt_us = -1L; u32 pkts_acked = 0; - u32 last_in_flight = 0; bool rtt_update; int flag = 0;
@@ -3257,7 +3256,6 @@ static int tcp_clean_rtx_queue(struct sock *sk, const struct sk_buff *ack_skb, if (!first_ackt) first_ackt = last_ackt; - last_in_flight = TCP_SKB_CB(skb)->tx.in_flight; if (before(start_seq, reord)) reord = start_seq; if (!after(scb->end_seq, tp->high_seq))
@@ -3323,8 +3321,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, const struct sk_buff *ack_skb, seq_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, first_ackt); ca_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, last_ackt); - if (pkts_acked == 1 && last_in_flight < tp->mss_cache && - last_in_flight && !prior_sacked && fully_acked && + if (pkts_acked == 1 && fully_acked && !prior_sacked && + (tp->snd_una - prior_snd_una) < tp->mss_cache && sack->rate->prior_delivered + 1 == tp->delivered && !(flag & (FLAG_CA_ALERT | FLAG_SYN_ACKED))) { /* Conservatively mark a delayed ACK. It's typically
@@ -3381,9 +3379,10 @@ static int tcp_clean_rtx_queue(struct sock *sk, const struct sk_buff *ack_skb, if (icsk->icsk_ca_ops->pkts_acked) { struct ack_sample sample = { .pkts_acked = pkts_acked, - .rtt_us = sack->rate->rtt_us, - .in_flight = last_in_flight }; + .rtt_us = sack->rate->rtt_us }; + sample.in_flight = tp->mss_cache * + (tp->delivered - sack->rate->prior_delivered); icsk->icsk_ca_ops->pkts_acked(sk, &sample); }
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 6d72f3ea48c4..fdc39b4fbbfa 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c@@ -1256,8 +1256,6 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache); skb->skb_mstamp_ns = tp->tcp_wstamp_ns; if (clone_it) { - TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq - - tp->snd_una; oskb = skb; tcp_skb_tsorted_save(oskb) {
diff --git a/net/ipv4/tcp_rate.c b/net/ipv4/tcp_rate.c
index 0de693565963..fbab921670cc 100644
--- a/net/ipv4/tcp_rate.c
+++ b/net/ipv4/tcp_rate.c@@ -65,6 +65,7 @@ void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb) TCP_SKB_CB(skb)->tx.first_tx_mstamp = tp->first_tx_mstamp; TCP_SKB_CB(skb)->tx.delivered_mstamp = tp->delivered_mstamp; TCP_SKB_CB(skb)->tx.delivered = tp->delivered; + TCP_SKB_CB(skb)->tx.delivered_ce = tp->delivered_ce; TCP_SKB_CB(skb)->tx.is_app_limited = tp->app_limited ? 1 : 0; }
@@ -86,6 +87,7 @@ void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb, if (!rs->prior_delivered || after(scb->tx.delivered, rs->prior_delivered)) { + rs->prior_delivered_ce = scb->tx.delivered_ce; rs->prior_delivered = scb->tx.delivered; rs->prior_mstamp = scb->tx.delivered_mstamp; rs->is_app_limited = scb->tx.is_app_limited;
@@ -138,6 +140,10 @@ void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost, } rs->delivered = tp->delivered - rs->prior_delivered; + rs->delivered_ce = tp->delivered_ce - rs->prior_delivered_ce; + /* delivered_ce occupies less than 32 bits in the skb control block */ + rs->delivered_ce &= TCPCB_DELIVERED_CE_MASK; + /* Model sending data and receiving ACKs as separate pipeline phases * for a window. Usually the ACK phase is longer, but with ACK * compression the send phase can be longer. To be safe we use the
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2.33.0.685.g46640cef36-goog