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tcp: tracking packets with CE marks in BW rate sample 

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 <brakmo@fb.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Luke Hsiao <lukehsiao@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yuchung Cheng 2021-09-23 21:17:07 +00:00 committed by David S. Miller
parent ae98f40d32
commit 40bc606379
4 changed files with 17 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
include/net/tcp.h
View File

@ -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 */

11
net/ipv4/tcp_input.c
View File

@ -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);
}

2
net/ipv4/tcp_output.c
View File

@ -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) {

6
net/ipv4/tcp_rate.c
View File

@ -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