diff options
Diffstat (limited to 'net/ipv4/tcp_rate.c')
| -rw-r--r-- | net/ipv4/tcp_rate.c | 209 |
1 files changed, 0 insertions, 209 deletions
diff --git a/net/ipv4/tcp_rate.c b/net/ipv4/tcp_rate.c deleted file mode 100644 index a8f6d9d06f2e..000000000000 --- a/net/ipv4/tcp_rate.c +++ /dev/null @@ -1,209 +0,0 @@ -// SPDX-License-Identifier: GPL-2.0-only -#include <net/tcp.h> - -/* The bandwidth estimator estimates the rate at which the network - * can currently deliver outbound data packets for this flow. At a high - * level, it operates by taking a delivery rate sample for each ACK. - * - * A rate sample records the rate at which the network delivered packets - * for this flow, calculated over the time interval between the transmission - * of a data packet and the acknowledgment of that packet. - * - * Specifically, over the interval between each transmit and corresponding ACK, - * the estimator generates a delivery rate sample. Typically it uses the rate - * at which packets were acknowledged. However, the approach of using only the - * acknowledgment rate faces a challenge under the prevalent ACK decimation or - * compression: packets can temporarily appear to be delivered much quicker - * than the bottleneck rate. Since it is physically impossible to do that in a - * sustained fashion, when the estimator notices that the ACK rate is faster - * than the transmit rate, it uses the latter: - * - * send_rate = #pkts_delivered/(last_snd_time - first_snd_time) - * ack_rate = #pkts_delivered/(last_ack_time - first_ack_time) - * bw = min(send_rate, ack_rate) - * - * Notice the estimator essentially estimates the goodput, not always the - * network bottleneck link rate when the sending or receiving is limited by - * other factors like applications or receiver window limits. The estimator - * deliberately avoids using the inter-packet spacing approach because that - * approach requires a large number of samples and sophisticated filtering. - * - * TCP flows can often be application-limited in request/response workloads. - * The estimator marks a bandwidth sample as application-limited if there - * was some moment during the sampled window of packets when there was no data - * ready to send in the write queue. - */ - -/* Snapshot the current delivery information in the skb, to generate - * a rate sample later when the skb is (s)acked in tcp_rate_skb_delivered(). - */ -void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb) -{ - struct tcp_sock *tp = tcp_sk(sk); - - /* In general we need to start delivery rate samples from the - * time we received the most recent ACK, to ensure we include - * the full time the network needs to deliver all in-flight - * packets. If there are no packets in flight yet, then we - * know that any ACKs after now indicate that the network was - * able to deliver those packets completely in the sampling - * interval between now and the next ACK. - * - * Note that we use packets_out instead of tcp_packets_in_flight(tp) - * because the latter is a guess based on RTO and loss-marking - * heuristics. We don't want spurious RTOs or loss markings to cause - * a spuriously small time interval, causing a spuriously high - * bandwidth estimate. - */ - if (!tp->packets_out) { - u64 tstamp_us = tcp_skb_timestamp_us(skb); - - tp->first_tx_mstamp = tstamp_us; - tp->delivered_mstamp = tstamp_us; - } - - 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; -} - -/* When an skb is sacked or acked, we fill in the rate sample with the (prior) - * delivery information when the skb was last transmitted. - * - * If an ACK (s)acks multiple skbs (e.g., stretched-acks), this function is - * called multiple times. We favor the information from the most recently - * sent skb, i.e., the skb with the most recently sent time and the highest - * sequence. - */ -void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb, - struct rate_sample *rs) -{ - struct tcp_sock *tp = tcp_sk(sk); - struct tcp_skb_cb *scb = TCP_SKB_CB(skb); - u64 tx_tstamp; - - if (!scb->tx.delivered_mstamp) - return; - - tx_tstamp = tcp_skb_timestamp_us(skb); - if (!rs->prior_delivered || - tcp_skb_sent_after(tx_tstamp, tp->first_tx_mstamp, - scb->end_seq, rs->last_end_seq)) { - 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; - rs->is_retrans = scb->sacked & TCPCB_RETRANS; - rs->last_end_seq = scb->end_seq; - - /* Record send time of most recently ACKed packet: */ - tp->first_tx_mstamp = tx_tstamp; - /* Find the duration of the "send phase" of this window: */ - rs->interval_us = tcp_stamp_us_delta(tp->first_tx_mstamp, - scb->tx.first_tx_mstamp); - - } - /* Mark off the skb delivered once it's sacked to avoid being - * used again when it's cumulatively acked. For acked packets - * we don't need to reset since it'll be freed soon. - */ - if (scb->sacked & TCPCB_SACKED_ACKED) - scb->tx.delivered_mstamp = 0; -} - -/* Update the connection delivery information and generate a rate sample. */ -void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost, - bool is_sack_reneg, struct rate_sample *rs) -{ - struct tcp_sock *tp = tcp_sk(sk); - u32 snd_us, ack_us; - - /* Clear app limited if bubble is acked and gone. */ - if (tp->app_limited && after(tp->delivered, tp->app_limited)) - tp->app_limited = 0; - - /* TODO: there are multiple places throughout tcp_ack() to get - * current time. Refactor the code using a new "tcp_acktag_state" - * to carry current time, flags, stats like "tcp_sacktag_state". - */ - if (delivered) - tp->delivered_mstamp = tp->tcp_mstamp; - - rs->acked_sacked = delivered; /* freshly ACKed or SACKed */ - rs->losses = lost; /* freshly marked lost */ - /* Return an invalid sample if no timing information is available or - * in recovery from loss with SACK reneging. Rate samples taken during - * a SACK reneging event may overestimate bw by including packets that - * were SACKed before the reneg. - */ - if (!rs->prior_mstamp || is_sack_reneg) { - rs->delivered = -1; - rs->interval_us = -1; - return; - } - 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 - * longer phase. - */ - snd_us = rs->interval_us; /* send phase */ - ack_us = tcp_stamp_us_delta(tp->tcp_mstamp, - rs->prior_mstamp); /* ack phase */ - rs->interval_us = max(snd_us, ack_us); - - /* Record both segment send and ack receive intervals */ - rs->snd_interval_us = snd_us; - rs->rcv_interval_us = ack_us; - - /* Normally we expect interval_us >= min-rtt. - * Note that rate may still be over-estimated when a spuriously - * retransmistted skb was first (s)acked because "interval_us" - * is under-estimated (up to an RTT). However continuously - * measuring the delivery rate during loss recovery is crucial - * for connections suffer heavy or prolonged losses. - */ - if (unlikely(rs->interval_us < tcp_min_rtt(tp))) { - if (!rs->is_retrans) - pr_debug("tcp rate: %ld %d %u %u %u\n", - rs->interval_us, rs->delivered, - inet_csk(sk)->icsk_ca_state, - tp->rx_opt.sack_ok, tcp_min_rtt(tp)); - rs->interval_us = -1; - return; - } - - /* Record the last non-app-limited or the highest app-limited bw */ - if (!rs->is_app_limited || - ((u64)rs->delivered * tp->rate_interval_us >= - (u64)tp->rate_delivered * rs->interval_us)) { - tp->rate_delivered = rs->delivered; - tp->rate_interval_us = rs->interval_us; - tp->rate_app_limited = rs->is_app_limited; - } -} - -/* If a gap is detected between sends, mark the socket application-limited. */ -void tcp_rate_check_app_limited(struct sock *sk) -{ - struct tcp_sock *tp = tcp_sk(sk); - - if (/* We have less than one packet to send. */ - tp->write_seq - tp->snd_nxt < tp->mss_cache && - /* Nothing in sending host's qdisc queues or NIC tx queue. */ - sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1) && - /* We are not limited by CWND. */ - tcp_packets_in_flight(tp) < tcp_snd_cwnd(tp) && - /* All lost packets have been retransmitted. */ - tp->lost_out <= tp->retrans_out) - tp->app_limited = - (tp->delivered + tcp_packets_in_flight(tp)) ? : 1; -} -EXPORT_SYMBOL_GPL(tcp_rate_check_app_limited); |