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Message-ID: <CANn89i+xRVxqx1-tSQaf_Kh7AG07Y2niGROPc0--mGf7_wz7Qw@mail.gmail.com> Date: Tue, 30 May 2023 09:09:32 +0200 From: Eric Dumazet <edumazet@...gle.com> To: Jason Xing <kerneljasonxing@...il.com> Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, dsahern@...nel.org, ncardwell@...gle.com, ycheng@...gle.com, toke@...e.dk, fuyuanli@...iglobal.com, netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com> Subject: Re: [PATCH net-next] tcp: handle the deferred sack compression when it should be canceled On Tue, May 30, 2023 at 4:37 AM Jason Xing <kerneljasonxing@...il.com> wrote: > > From: Jason Xing <kernelxing@...cent.com> > > In the previous commits, we have not implemented to deal with the case > where we're going to abort sending a ack triggered in the timer. So > introducing a new flag ICSK_ACK_COMP_TIMER for sack compression only > could satisify this requirement. > Sorry, I can not parse this changelog. What is the problem you want to fix ? > Signed-off-by: Jason Xing <kernelxing@...cent.com> > --- > Comment on this: > This patch is based on top of a commit[1]. I don't think the current > patch is fixing a bug, but more like an improvement. So I would like > to target at net-next tree. > > [1]: https://patchwork.kernel.org/project/netdevbpf/patch/20230529113804.GA20300@didi-ThinkCentre-M920t-N000/ > --- > include/net/inet_connection_sock.h | 3 ++- > net/ipv4/tcp_input.c | 6 +++++- > net/ipv4/tcp_output.c | 3 +++ > net/ipv4/tcp_timer.c | 5 ++++- > 4 files changed, 14 insertions(+), 3 deletions(-) > > diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h > index c2b15f7e5516..34ff6d27471d 100644 > --- a/include/net/inet_connection_sock.h > +++ b/include/net/inet_connection_sock.h > @@ -164,7 +164,8 @@ enum inet_csk_ack_state_t { > ICSK_ACK_TIMER = 2, > ICSK_ACK_PUSHED = 4, > ICSK_ACK_PUSHED2 = 8, > - ICSK_ACK_NOW = 16 /* Send the next ACK immediately (once) */ > + ICSK_ACK_NOW = 16, /* Send the next ACK immediately (once) */ > + ICSK_ACK_COMP_TIMER = 32 /* Used for sack compression */ > }; > > void inet_csk_init_xmit_timers(struct sock *sk, > diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c > index cc072d2cfcd8..3980f77dcdff 100644 > --- a/net/ipv4/tcp_input.c > +++ b/net/ipv4/tcp_input.c > @@ -4540,6 +4540,9 @@ static void tcp_sack_compress_send_ack(struct sock *sk) > if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1) > __sock_put(sk); > > + /* It also deal with the case where the sack compression is deferred */ > + inet_csk(sk)->icsk_ack.pending &= ~ICSK_ACK_COMP_TIMER; > + > /* Since we have to send one ack finally, > * substract one from tp->compressed_ack to keep > * LINUX_MIB_TCPACKCOMPRESSED accurate. > @@ -5555,7 +5558,7 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) > goto send_now; > } > tp->compressed_ack++; > - if (hrtimer_is_queued(&tp->compressed_ack_timer)) > + if (inet_csk(sk)->icsk_ack.pending & ICSK_ACK_COMP_TIMER) > return; I do not see why adding a new bit, while hrtimer() already has one ? > > /* compress ack timer : 5 % of rtt, but no more than tcp_comp_sack_delay_ns */ > @@ -5568,6 +5571,7 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) > READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_comp_sack_delay_ns), > rtt * (NSEC_PER_USEC >> 3)/20); > sock_hold(sk); > + inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_COMP_TIMER; > hrtimer_start_range_ns(&tp->compressed_ack_timer, ns_to_ktime(delay), > READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_comp_sack_slack_ns), > HRTIMER_MODE_REL_PINNED_SOFT); > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c > index 02b58721ab6b..83840daad142 100644 > --- a/net/ipv4/tcp_output.c > +++ b/net/ipv4/tcp_output.c > @@ -188,6 +188,9 @@ static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts, > tp->compressed_ack = 0; > if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1) > __sock_put(sk); > + > + /* It also deal with the case where the sack compression is deferred */ > + inet_csk(sk)->icsk_ack.pending &= ~ICSK_ACK_COMP_TIMER; This is adding a lot of code in fast path. > } > > if (unlikely(rcv_nxt != tp->rcv_nxt)) > diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c > index b3f8933b347c..a970336d1383 100644 > --- a/net/ipv4/tcp_timer.c > +++ b/net/ipv4/tcp_timer.c > @@ -323,9 +323,12 @@ void tcp_compack_timer_handler(struct sock *sk) > { > struct tcp_sock *tp = tcp_sk(sk); > > - if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))) > + if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || > + !(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_COMP_TIMER)) > return; > > + inet_csk(sk)->icsk_ack.pending &= ~ICSK_ACK_COMP_TIMER; > + > if (tp->compressed_ack) { > /* Since we have to send one ack finally, > * subtract one from tp->compressed_ack to keep > -- > 2.37.3 > An ACK is an ACK, I do not see why you need to differentiate them.
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