From 45f119bf936b1f9f546a0b139c5b56f9bb2bdc78 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Sun, 30 Jul 2017 03:57:21 +0200 Subject: [PATCH] tcp: remove header prediction Like prequeue, I am not sure this is overly useful nowadays. If we receive a train of packets, GRO will aggregate them if the headers are the same (HP predates GRO by several years) so we don't get a per-packet benefit, only a per-aggregated-packet one. Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- include/linux/tcp.h | 6 -- include/net/tcp.h | 23 ----- net/ipv4/tcp.c | 4 +- net/ipv4/tcp_input.c | 192 ++------------------------------------- net/ipv4/tcp_minisocks.c | 2 - net/ipv4/tcp_output.c | 2 - 6 files changed, 10 insertions(+), 219 deletions(-) diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 32fb37cfb0d1..d7389ea36e10 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -147,12 +147,6 @@ struct tcp_sock { u16 tcp_header_len; /* Bytes of tcp header to send */ u16 gso_segs; /* Max number of segs per GSO packet */ -/* - * Header prediction flags - * 0x5?10 << 16 + snd_wnd in net byte order - */ - __be32 pred_flags; - /* * RFC793 variables by their proper names. This means you can * read the code and the spec side by side (and laugh ...) diff --git a/include/net/tcp.h b/include/net/tcp.h index 8507c81fb0e9..8f11b82b5b5a 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -631,29 +631,6 @@ static inline u32 __tcp_set_rto(const struct tcp_sock *tp) return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us); } -static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd) -{ - tp->pred_flags = htonl((tp->tcp_header_len << 26) | - ntohl(TCP_FLAG_ACK) | - snd_wnd); -} - -static inline void tcp_fast_path_on(struct tcp_sock *tp) -{ - __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale); -} - -static inline void tcp_fast_path_check(struct sock *sk) -{ - struct tcp_sock *tp = tcp_sk(sk); - - if (RB_EMPTY_ROOT(&tp->out_of_order_queue) && - tp->rcv_wnd && - atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf && - !tp->urg_data) - tcp_fast_path_on(tp); -} - /* Compute the actual rto_min value */ static inline u32 tcp_rto_min(struct sock *sk) { diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 62018ea6f45f..e022874d509f 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1848,10 +1848,8 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock, tcp_rcv_space_adjust(sk); skip_copy: - if (tp->urg_data && after(tp->copied_seq, tp->urg_seq)) { + if (tp->urg_data && after(tp->copied_seq, tp->urg_seq)) tp->urg_data = 0; - tcp_fast_path_check(sk); - } if (used + offset < skb->len) continue; diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 87efde9f5a90..bfde9d7d210e 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -103,7 +103,6 @@ int sysctl_tcp_invalid_ratelimit __read_mostly = HZ/2; #define FLAG_DATA_SACKED 0x20 /* New SACK. */ #define FLAG_ECE 0x40 /* ECE in this ACK */ #define FLAG_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */ -#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */ #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */ #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */ @@ -3367,12 +3366,6 @@ static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32 if (tp->snd_wnd != nwin) { tp->snd_wnd = nwin; - /* Note, it is the only place, where - * fast path is recovered for sending TCP. - */ - tp->pred_flags = 0; - tcp_fast_path_check(sk); - if (tcp_send_head(sk)) tcp_slow_start_after_idle_check(sk); @@ -3597,19 +3590,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) if (flag & FLAG_UPDATE_TS_RECENT) tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); - if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) { - /* Window is constant, pure forward advance. - * No more checks are required. - * Note, we use the fact that SND.UNA>=SND.WL2. - */ - tcp_update_wl(tp, ack_seq); - tcp_snd_una_update(tp, ack); - flag |= FLAG_WIN_UPDATE; - - tcp_in_ack_event(sk, CA_ACK_WIN_UPDATE); - - NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPACKS); - } else { + { u32 ack_ev_flags = CA_ACK_SLOWPATH; if (ack_seq != TCP_SKB_CB(skb)->end_seq) @@ -4398,8 +4379,6 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb) return; } - /* Disable header prediction. */ - tp->pred_flags = 0; inet_csk_schedule_ack(sk); NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOQUEUE); @@ -4638,8 +4617,6 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) if (tp->rx_opt.num_sacks) tcp_sack_remove(tp); - tcp_fast_path_check(sk); - if (eaten > 0) kfree_skb_partial(skb, fragstolen); if (!sock_flag(sk, SOCK_DEAD)) @@ -4965,7 +4942,6 @@ static int tcp_prune_queue(struct sock *sk) NET_INC_STATS(sock_net(sk), LINUX_MIB_RCVPRUNED); /* Massive buffer overcommit. */ - tp->pred_flags = 0; return -1; } @@ -5137,9 +5113,6 @@ static void tcp_check_urg(struct sock *sk, const struct tcphdr *th) tp->urg_data = TCP_URG_NOTYET; tp->urg_seq = ptr; - - /* Disable header prediction. */ - tp->pred_flags = 0; } /* This is the 'fast' part of urgent handling. */ @@ -5298,26 +5271,6 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, /* * TCP receive function for the ESTABLISHED state. - * - * It is split into a fast path and a slow path. The fast path is - * disabled when: - * - A zero window was announced from us - zero window probing - * is only handled properly in the slow path. - * - Out of order segments arrived. - * - Urgent data is expected. - * - There is no buffer space left - * - Unexpected TCP flags/window values/header lengths are received - * (detected by checking the TCP header against pred_flags) - * - Data is sent in both directions. Fast path only supports pure senders - * or pure receivers (this means either the sequence number or the ack - * value must stay constant) - * - Unexpected TCP option. - * - * When these conditions are not satisfied it drops into a standard - * receive procedure patterned after RFC793 to handle all cases. - * The first three cases are guaranteed by proper pred_flags setting, - * the rest is checked inline. Fast processing is turned on in - * tcp_data_queue when everything is OK. */ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb, const struct tcphdr *th) @@ -5328,144 +5281,19 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb, tcp_mstamp_refresh(tp); if (unlikely(!sk->sk_rx_dst)) inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb); - /* - * Header prediction. - * The code loosely follows the one in the famous - * "30 instruction TCP receive" Van Jacobson mail. - * - * Van's trick is to deposit buffers into socket queue - * on a device interrupt, to call tcp_recv function - * on the receive process context and checksum and copy - * the buffer to user space. smart... - * - * Our current scheme is not silly either but we take the - * extra cost of the net_bh soft interrupt processing... - * We do checksum and copy also but from device to kernel. - */ tp->rx_opt.saw_tstamp = 0; - /* pred_flags is 0xS?10 << 16 + snd_wnd - * if header_prediction is to be made - * 'S' will always be tp->tcp_header_len >> 2 - * '?' will be 0 for the fast path, otherwise pred_flags is 0 to - * turn it off (when there are holes in the receive - * space for instance) - * PSH flag is ignored. - */ - - if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && - TCP_SKB_CB(skb)->seq == tp->rcv_nxt && - !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) { - int tcp_header_len = tp->tcp_header_len; - - /* Timestamp header prediction: tcp_header_len - * is automatically equal to th->doff*4 due to pred_flags - * match. - */ - - /* Check timestamp */ - if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { - /* No? Slow path! */ - if (!tcp_parse_aligned_timestamp(tp, th)) - goto slow_path; - - /* If PAWS failed, check it more carefully in slow path */ - if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) - goto slow_path; - - /* DO NOT update ts_recent here, if checksum fails - * and timestamp was corrupted part, it will result - * in a hung connection since we will drop all - * future packets due to the PAWS test. - */ - } - - if (len <= tcp_header_len) { - /* Bulk data transfer: sender */ - if (len == tcp_header_len) { - /* Predicted packet is in window by definition. - * seq == rcv_nxt and rcv_wup <= rcv_nxt. - * Hence, check seq<=rcv_wup reduces to: - */ - if (tcp_header_len == - (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && - tp->rcv_nxt == tp->rcv_wup) - tcp_store_ts_recent(tp); - - /* We know that such packets are checksummed - * on entry. - */ - tcp_ack(sk, skb, 0); - __kfree_skb(skb); - tcp_data_snd_check(sk); - return; - } else { /* Header too small */ - TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS); - goto discard; - } - } else { - int eaten = 0; - bool fragstolen = false; - - if (tcp_checksum_complete(skb)) - goto csum_error; - - if ((int)skb->truesize > sk->sk_forward_alloc) - goto step5; - - /* Predicted packet is in window by definition. - * seq == rcv_nxt and rcv_wup <= rcv_nxt. - * Hence, check seq<=rcv_wup reduces to: - */ - if (tcp_header_len == - (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && - tp->rcv_nxt == tp->rcv_wup) - tcp_store_ts_recent(tp); - - tcp_rcv_rtt_measure_ts(sk, skb); - - NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPHITS); - - /* Bulk data transfer: receiver */ - eaten = tcp_queue_rcv(sk, skb, tcp_header_len, - &fragstolen); - - tcp_event_data_recv(sk, skb); - - if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { - /* Well, only one small jumplet in fast path... */ - tcp_ack(sk, skb, FLAG_DATA); - tcp_data_snd_check(sk); - if (!inet_csk_ack_scheduled(sk)) - goto no_ack; - } - - __tcp_ack_snd_check(sk, 0); -no_ack: - if (eaten) - kfree_skb_partial(skb, fragstolen); - sk->sk_data_ready(sk); - return; - } - } - -slow_path: if (len < (th->doff << 2) || tcp_checksum_complete(skb)) goto csum_error; if (!th->ack && !th->rst && !th->syn) goto discard; - /* - * Standard slow path. - */ - if (!tcp_validate_incoming(sk, skb, th, 1)) return; -step5: - if (tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT) < 0) + if (tcp_ack(sk, skb, FLAG_UPDATE_TS_RECENT) < 0) goto discard; tcp_rcv_rtt_measure_ts(sk, skb); @@ -5519,11 +5347,10 @@ void tcp_finish_connect(struct sock *sk, struct sk_buff *skb) if (sock_flag(sk, SOCK_KEEPOPEN)) inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); - if (!tp->rx_opt.snd_wscale) - __tcp_fast_path_on(tp, tp->snd_wnd); - else - tp->pred_flags = 0; - + if (!sock_flag(sk, SOCK_DEAD)) { + sk->sk_state_change(sk); + sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT); + } } static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack, @@ -5652,7 +5479,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, tcp_ecn_rcv_synack(tp, th); tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); - tcp_ack(sk, skb, FLAG_SLOWPATH); + tcp_ack(sk, skb, 0); /* Ok.. it's good. Set up sequence numbers and * move to established. @@ -5888,8 +5715,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) return 0; /* step 5: check the ACK field */ - acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH | - FLAG_UPDATE_TS_RECENT | + + acceptable = tcp_ack(sk, skb, FLAG_UPDATE_TS_RECENT | FLAG_NO_CHALLENGE_ACK) > 0; if (!acceptable) { @@ -5957,7 +5784,6 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) tp->lsndtime = tcp_jiffies32; tcp_initialize_rcv_mss(sk); - tcp_fast_path_on(tp); break; case TCP_FIN_WAIT1: { diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 188a6f31356d..1537b87c657f 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -436,8 +436,6 @@ struct sock *tcp_create_openreq_child(const struct sock *sk, struct tcp_sock *newtp = tcp_sk(newsk); /* Now setup tcp_sock */ - newtp->pred_flags = 0; - newtp->rcv_wup = newtp->copied_seq = newtp->rcv_nxt = treq->rcv_isn + 1; newtp->segs_in = 1; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 886d874775df..8380464aead1 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -295,9 +295,7 @@ static u16 tcp_select_window(struct sock *sk) /* RFC1323 scaling applied */ new_win >>= tp->rx_opt.rcv_wscale; - /* If we advertise zero window, disable fast path. */ if (new_win == 0) { - tp->pred_flags = 0; if (old_win) NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTOZEROWINDOWADV); -- GitLab