| Message ID | 20200930125457.1579469-1-eric.dumazet@gmail.com |
|---|---|
| Headers | show |
| Series | tcp: exponential backoff in tcp_send_ack() | expand |
On Wed, Sep 30, 2020 at 8:55 AM Eric Dumazet <eric.dumazet@gmail.com> wrote: > > From: Eric Dumazet <edumazet@google.com> > > TCP has been using it to work around the possibility of tcp_delack_timer() > finding the socket owned by user. > > After commit 6f458dfb4092 ("tcp: improve latencies of timer triggered events") > we added TCP_DELACK_TIMER_DEFERRED atomic bit for more immediate recovery, > so we can get rid of icsk_ack.blocked > > This frees space that following patch will reuse. > > Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> > --- > include/net/inet_connection_sock.h | 4 ++-- > net/dccp/timer.c | 1 - > net/ipv4/inet_connection_sock.c | 2 +- > net/ipv4/tcp.c | 6 ++---- > net/ipv4/tcp_output.c | 7 ++----- > net/ipv4/tcp_timer.c | 1 - > 6 files changed, 7 insertions(+), 14 deletions(-) > > diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h > index dc763ca9413cc9c6279a59f9d1776cf2dbb1e853..79875f976190750819948425e63dd0309c699050 100644 > --- a/include/net/inet_connection_sock.h > +++ b/include/net/inet_connection_sock.h > @@ -110,7 +110,7 @@ struct inet_connection_sock { > __u8 pending; /* ACK is pending */ > __u8 quick; /* Scheduled number of quick acks */ > __u8 pingpong; /* The session is interactive */ > - __u8 blocked; /* Delayed ACK was blocked by socket lock */ > + /* one byte hole. */ > __u32 ato; /* Predicted tick of soft clock */ > unsigned long timeout; /* Currently scheduled timeout */ > __u32 lrcvtime; /* timestamp of last received data packet */ > @@ -198,7 +198,7 @@ static inline void inet_csk_clear_xmit_timer(struct sock *sk, const int what) > sk_stop_timer(sk, &icsk->icsk_retransmit_timer); > #endif > } else if (what == ICSK_TIME_DACK) { > - icsk->icsk_ack.blocked = icsk->icsk_ack.pending = 0; > + icsk->icsk_ack.pending = 0; > #ifdef INET_CSK_CLEAR_TIMERS > sk_stop_timer(sk, &icsk->icsk_delack_timer); > #endif > diff --git a/net/dccp/timer.c b/net/dccp/timer.c > index 927c796d76825439a35c4deb3fb2e45e4313f9b3..a934d293237366aeca87bd3c32241880639291c5 100644 > --- a/net/dccp/timer.c > +++ b/net/dccp/timer.c > @@ -176,7 +176,6 @@ static void dccp_delack_timer(struct timer_list *t) > bh_lock_sock(sk); > if (sock_owned_by_user(sk)) { > /* Try again later. */ > - icsk->icsk_ack.blocked = 1; > __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); > sk_reset_timer(sk, &icsk->icsk_delack_timer, > jiffies + TCP_DELACK_MIN); > diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c > index b457dd2d6c75b2f63bc7849474ac909adb14d603..4148f5f78f313cde1e0596b9eb3696df16e3f990 100644 > --- a/net/ipv4/inet_connection_sock.c > +++ b/net/ipv4/inet_connection_sock.c > @@ -564,7 +564,7 @@ void inet_csk_clear_xmit_timers(struct sock *sk) > { > struct inet_connection_sock *icsk = inet_csk(sk); > > - icsk->icsk_pending = icsk->icsk_ack.pending = icsk->icsk_ack.blocked = 0; > + icsk->icsk_pending = icsk->icsk_ack.pending = 0; > > sk_stop_timer(sk, &icsk->icsk_retransmit_timer); > sk_stop_timer(sk, &icsk->icsk_delack_timer); > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c > index 2a8bfa89a5159837e3687e4e0f8cddba7fe54899..ed2805564424a90f003eed867bbed7f5ac4ae833 100644 > --- a/net/ipv4/tcp.c > +++ b/net/ipv4/tcp.c > @@ -1538,10 +1538,8 @@ void tcp_cleanup_rbuf(struct sock *sk, int copied) > > if (inet_csk_ack_scheduled(sk)) { > const struct inet_connection_sock *icsk = inet_csk(sk); > - /* Delayed ACKs frequently hit locked sockets during bulk > - * receive. */ > - if (icsk->icsk_ack.blocked || > - /* Once-per-two-segments ACK was not sent by tcp_input.c */ > + > + if (/* Once-per-two-segments ACK was not sent by tcp_input.c */ > tp->rcv_nxt - tp->rcv_wup > icsk->icsk_ack.rcv_mss || > /* > * If this read emptied read buffer, we send ACK, if > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c > index 386978dcd318d84af486d0d1a5bb1786f4a493cf..6bd4e383030ea20441332a30e98fbda8cd90f84a 100644 > --- a/net/ipv4/tcp_output.c > +++ b/net/ipv4/tcp_output.c > @@ -3911,11 +3911,8 @@ void tcp_send_delayed_ack(struct sock *sk) > > /* Use new timeout only if there wasn't a older one earlier. */ > if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) { > - /* If delack timer was blocked or is about to expire, > - * send ACK now. > - */ > - if (icsk->icsk_ack.blocked || > - time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) { > + /* If delack timer is about to expire, send ACK now. */ > + if (time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) { > tcp_send_ack(sk); > return; > } > diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c > index 0c08c420fbc21a98dedf72148ea2a6f85bf3ff7a..6c62b9ea1320d9bbd26ed86b9f41de02fee6c491 100644 > --- a/net/ipv4/tcp_timer.c > +++ b/net/ipv4/tcp_timer.c > @@ -331,7 +331,6 @@ static void tcp_delack_timer(struct timer_list *t) > if (!sock_owned_by_user(sk)) { > tcp_delack_timer_handler(sk); > } else { > - icsk->icsk_ack.blocked = 1; > __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); > /* deleguate our work to tcp_release_cb() */ > if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags)) > -- > 2.28.0.806.g8561365e88-goog >
From: Eric Dumazet <eric.dumazet@gmail.com> Date: Wed, 30 Sep 2020 05:54:55 -0700 > We had outages caused by repeated skb allocation failures in tcp_send_ack() > > It is time to add exponential backoff to reduce number of attempts. > Before doing so, first patch removes icsk_ack.blocked to make > room for a new field (icsk_ack.retry) Series applied, thanks Eric.
From: Eric Dumazet <edumazet@google.com> We had outages caused by repeated skb allocation failures in tcp_send_ack() It is time to add exponential backoff to reduce number of attempts. Before doing so, first patch removes icsk_ack.blocked to make room for a new field (icsk_ack.retry) Eric Dumazet (2): inet: remove icsk_ack.blocked tcp: add exponential backoff in __tcp_send_ack() include/net/inet_connection_sock.h | 5 +++-- net/dccp/timer.c | 1 - net/ipv4/inet_connection_sock.c | 2 +- net/ipv4/tcp.c | 6 ++---- net/ipv4/tcp_output.c | 18 ++++++++++-------- net/ipv4/tcp_timer.c | 1 - 6 files changed, 16 insertions(+), 17 deletions(-)