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Date: Wed, 17 May 2017 09:42:55 -0400
From: Soheil Hassas Yeganeh <soheil@...gle.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>,
Neal Cardwell <ncardwell@...gle.com>,
Yuchung Cheng <ycheng@...gle.com>,
Wei Wang <weiwan@...gle.com>, netdev <netdev@...r.kernel.org>,
Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH net-next 01/15] tcp: use tp->tcp_mstamp in output path
On Tue, May 16, 2017 at 5:00 PM, Eric Dumazet <edumazet@...gle.com> wrote:
> Idea is to later convert tp->tcp_mstamp to a full u64 counter
> using usec resolution, so that we can later have fine
> grained TCP TS clock (RFC 7323), regardless of HZ value.
>
> We try to refresh tp->tcp_mstamp only when necessary.
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>
> ---
> net/ipv4/tcp_ipv4.c | 1 +
> net/ipv4/tcp_output.c | 21 +++++++++++----------
> net/ipv4/tcp_recovery.c | 1 -
> net/ipv4/tcp_timer.c | 3 ++-
> 4 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index 5ab2aac5ca191075383fc75214da816873bb222c..d8fe25db79f223e3fde85882effd2ac6ec15f8ca 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -483,6 +483,7 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
> skb = tcp_write_queue_head(sk);
> BUG_ON(!skb);
>
> + skb_mstamp_get(&tp->tcp_mstamp);
> remaining = icsk->icsk_rto -
> min(icsk->icsk_rto,
> tcp_time_stamp - tcp_skb_timestamp(skb));
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index a32172d69a03cbe76b45ec3094222f6c3a73e27d..4c8a6eaba6b39a2aea061dd6857ed8df954c5ca2 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -997,8 +997,8 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
> BUG_ON(!skb || !tcp_skb_pcount(skb));
> tp = tcp_sk(sk);
>
> + skb->skb_mstamp = tp->tcp_mstamp;
> if (clone_it) {
> - skb_mstamp_get(&skb->skb_mstamp);
> TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
> - tp->snd_una;
> tcp_rate_skb_sent(sk, skb);
> @@ -1906,7 +1906,6 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
> const struct inet_connection_sock *icsk = inet_csk(sk);
> u32 age, send_win, cong_win, limit, in_flight;
> struct tcp_sock *tp = tcp_sk(sk);
> - struct skb_mstamp now;
> struct sk_buff *head;
> int win_divisor;
>
> @@ -1962,8 +1961,8 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
> }
>
> head = tcp_write_queue_head(sk);
> - skb_mstamp_get(&now);
> - age = skb_mstamp_us_delta(&now, &head->skb_mstamp);
> +
> + age = skb_mstamp_us_delta(&tp->tcp_mstamp, &head->skb_mstamp);
> /* If next ACK is likely to come too late (half srtt), do not defer */
> if (age < (tp->srtt_us >> 4))
> goto send_now;
> @@ -2280,6 +2279,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
> }
>
> max_segs = tcp_tso_segs(sk, mss_now);
> + skb_mstamp_get(&tp->tcp_mstamp);
> while ((skb = tcp_send_head(sk))) {
> unsigned int limit;
>
> @@ -2291,7 +2291,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
>
> if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
> /* "skb_mstamp" is used as a start point for the retransmit timer */
> - skb_mstamp_get(&skb->skb_mstamp);
> + skb->skb_mstamp = tp->tcp_mstamp;
> goto repair; /* Skip network transmission */
> }
>
> @@ -2879,7 +2879,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
> skb_headroom(skb) >= 0xFFFF)) {
> struct sk_buff *nskb;
>
> - skb_mstamp_get(&skb->skb_mstamp);
> + skb->skb_mstamp = tp->tcp_mstamp;
> nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
> err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
> -ENOBUFS;
> @@ -3095,7 +3095,7 @@ void tcp_send_active_reset(struct sock *sk, gfp_t priority)
> skb_reserve(skb, MAX_TCP_HEADER);
> tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
> TCPHDR_ACK | TCPHDR_RST);
> - skb_mstamp_get(&skb->skb_mstamp);
> + skb_mstamp_get(&tcp_sk(sk)->tcp_mstamp);
> /* Send it off. */
> if (tcp_transmit_skb(sk, skb, 0, priority))
> NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
> @@ -3453,7 +3453,8 @@ int tcp_connect(struct sock *sk)
> return -ENOBUFS;
>
> tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
> - tp->retrans_stamp = tcp_time_stamp;
> + skb_mstamp_get(&tp->tcp_mstamp);
> + tp->retrans_stamp = tp->tcp_mstamp.stamp_jiffies;
> tcp_connect_queue_skb(sk, buff);
> tcp_ecn_send_syn(sk, buff);
>
> @@ -3572,7 +3573,6 @@ void tcp_send_ack(struct sock *sk)
> skb_set_tcp_pure_ack(buff);
>
> /* Send it off, this clears delayed acks for us. */
> - skb_mstamp_get(&buff->skb_mstamp);
> tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
> }
> EXPORT_SYMBOL_GPL(tcp_send_ack);
> @@ -3606,15 +3606,16 @@ static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
> * send it.
> */
> tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
> - skb_mstamp_get(&skb->skb_mstamp);
> NET_INC_STATS(sock_net(sk), mib);
> return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
> }
>
> +/* Called from setsockopt( ... TCP_REPAIR ) */
> void tcp_send_window_probe(struct sock *sk)
> {
> if (sk->sk_state == TCP_ESTABLISHED) {
> tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
> + skb_mstamp_get(&tcp_sk(sk)->tcp_mstamp);
> tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
> }
> }
> diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c
> index 362b8c75bfab44cf87c2a01398a146a271bc1119..cd72b3d3879e88181c8a4639f0334a24e4cda852 100644
> --- a/net/ipv4/tcp_recovery.c
> +++ b/net/ipv4/tcp_recovery.c
> @@ -166,7 +166,6 @@ void tcp_rack_reo_timeout(struct sock *sk)
> u32 timeout, prior_inflight;
>
> prior_inflight = tcp_packets_in_flight(tp);
> - skb_mstamp_get(&tp->tcp_mstamp);
> tcp_rack_detect_loss(sk, &timeout);
> if (prior_inflight != tcp_packets_in_flight(tp)) {
> if (inet_csk(sk)->icsk_ca_state != TCP_CA_Recovery) {
> diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
> index 86934bcf685a65ec3af3d22f1801ffa33eea76e2..ec7c5473c788d77ae459b38492f2f2606d00d1ba 100644
> --- a/net/ipv4/tcp_timer.c
> +++ b/net/ipv4/tcp_timer.c
> @@ -339,7 +339,7 @@ static void tcp_probe_timer(struct sock *sk)
> */
> start_ts = tcp_skb_timestamp(tcp_send_head(sk));
> if (!start_ts)
> - skb_mstamp_get(&tcp_send_head(sk)->skb_mstamp);
> + tcp_send_head(sk)->skb_mstamp = tp->tcp_mstamp;
> else if (icsk->icsk_user_timeout &&
> (s32)(tcp_time_stamp - start_ts) > icsk->icsk_user_timeout)
> goto abort;
> @@ -561,6 +561,7 @@ void tcp_write_timer_handler(struct sock *sk)
> goto out;
> }
>
> + skb_mstamp_get(&tcp_sk(sk)->tcp_mstamp);
> event = icsk->icsk_pending;
>
> switch (event) {
> --
> 2.13.0.303.g4ebf302169-goog
>
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