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Message-ID: <CAK6E8=eNe8Ce9zKXx1rKBL48XuDVGntAOOtKVi6ywgMjafMWXg@mail.gmail.com> Date: Tue, 30 Aug 2022 22:58:33 -0700 From: Yuchung Cheng <ycheng@...gle.com> To: Yonglong Li <liyonglong@...natelecom.cn> Cc: netdev@...r.kernel.org, davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, Neal Cardwell <ncardwell@...gle.com> Subject: Re: [PATCH] tcp: del skb from tsorted_sent_queue after mark it as lost On Mon, Aug 29, 2022 at 5:23 PM Yuchung Cheng <ycheng@...gle.com> wrote: > > On Mon, Aug 29, 2022 at 1:21 AM Yonglong Li <liyonglong@...natelecom.cn> wrote: > > > > if rack is enabled, when skb marked as lost we can remove it from > > tsorted_sent_queue. It will reduces the iterations on tsorted_sent_queue > > in tcp_rack_detect_loss > > Did you test the case where an skb is marked lost again after > retransmission? I can't quite remember the reason I avoided this > optimization. let me run some test and get back to you. As I suspected, this patch fails to pass our packet drill tests. It breaks detecting retransmitted packets that get lost again, b/c they have already been removed from the tsorted list when they get lost the first time. > > > > > > Signed-off-by: Yonglong Li <liyonglong@...natelecom.cn> > > --- > > net/ipv4/tcp_input.c | 15 +++++++++------ > > net/ipv4/tcp_recovery.c | 1 - > > 2 files changed, 9 insertions(+), 7 deletions(-) > > > > diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c > > index ab5f0ea..01bd644 100644 > > --- a/net/ipv4/tcp_input.c > > +++ b/net/ipv4/tcp_input.c > > @@ -1082,6 +1082,12 @@ static void tcp_notify_skb_loss_event(struct tcp_sock *tp, const struct sk_buff > > tp->lost += tcp_skb_pcount(skb); > > } > > > > +static bool tcp_is_rack(const struct sock *sk) > > +{ > > + return READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) & > > + TCP_RACK_LOSS_DETECTION; > > +} > > + > > void tcp_mark_skb_lost(struct sock *sk, struct sk_buff *skb) > > { > > __u8 sacked = TCP_SKB_CB(skb)->sacked; > > @@ -1105,6 +1111,9 @@ void tcp_mark_skb_lost(struct sock *sk, struct sk_buff *skb) > > TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; > > tcp_notify_skb_loss_event(tp, skb); > > } > > + > > + if (tcp_is_rack(sk)) > > + list_del_init(&skb->tcp_tsorted_anchor); > > } > > > > /* Updates the delivered and delivered_ce counts */ > > @@ -2093,12 +2102,6 @@ static inline void tcp_init_undo(struct tcp_sock *tp) > > tp->undo_retrans = tp->retrans_out ? : -1; > > } > > > > -static bool tcp_is_rack(const struct sock *sk) > > -{ > > - return READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) & > > - TCP_RACK_LOSS_DETECTION; > > -} > > - > > /* If we detect SACK reneging, forget all SACK information > > * and reset tags completely, otherwise preserve SACKs. If receiver > > * dropped its ofo queue, we will know this due to reneging detection. > > diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c > > index 50abaa9..ba52ec9e 100644 > > --- a/net/ipv4/tcp_recovery.c > > +++ b/net/ipv4/tcp_recovery.c > > @@ -84,7 +84,6 @@ static void tcp_rack_detect_loss(struct sock *sk, u32 *reo_timeout) > > remaining = tcp_rack_skb_timeout(tp, skb, reo_wnd); > > if (remaining <= 0) { > > tcp_mark_skb_lost(sk, skb); > > - list_del_init(&skb->tcp_tsorted_anchor); > > } else { > > /* Record maximum wait time */ > > *reo_timeout = max_t(u32, *reo_timeout, remaining); > > -- > > 1.8.3.1 > >
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