[PATCH net-next] tcp: handle EOR and FIN conditions the same in tcp_tso_should_defer()

[PATCH net-next] tcp: handle EOR and FIN conditions the same in tcp_tso_should_defer()

[Eric Dumazet]

In commit f9bfe4e6a9d0 ("tcp: lack of available data can also cause
TSO defer") we moved the test in tcp_tso_should_defer() for packets
with a FIN flag, and we mentioned that the same would be done
later for EOR flag.

Both flags should be handled at the same time, after all other
heuristics have been considered. They both mean that no more bytes
can be added to this skb by an application.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp_output.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index c31badfee806a70d5af6dc033cf9155adb1f9375..730bc44dbad9363814705b28c2f91a2253d91207 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1947,10 +1947,6 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
 	if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
 		goto send_now;
 
-	/* If this packet won't get more data, do not wait. */
-	if (TCP_SKB_CB(skb)->eor)
-		goto send_now;
-
 	win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor);
 	if (win_divisor) {
 		u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
@@ -1999,7 +1995,8 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
 	}
 
 	/* If this packet won't get more data, do not wait. */
-	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
+	if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) ||
+	    TCP_SKB_CB(skb)->eor)
 		goto send_now;
 
 	return true;
-- 
2.20.0.rc2.403.gdbc3b29805-goog

Re: [PATCH net-next] tcp: handle EOR and FIN conditions the same in tcp_tso_should_defer()

[Soheil Hassas Yeganeh]

On Mon, Dec 10, 2018 at 9:10 AM Eric Dumazet <edumazet@google.com> wrote:
>
> In commit f9bfe4e6a9d0 ("tcp: lack of available data can also cause
> TSO defer") we moved the test in tcp_tso_should_defer() for packets
> with a FIN flag, and we mentioned that the same would be done
> later for EOR flag.
>
> Both flags should be handled at the same time, after all other
> heuristics have been considered. They both mean that no more bytes
> can be added to this skb by an application.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Acked-by: Soheil Hassas Yeganeh <soheil@google.com>

Thank you Eric for the patch!

> ---
>  net/ipv4/tcp_output.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index c31badfee806a70d5af6dc033cf9155adb1f9375..730bc44dbad9363814705b28c2f91a2253d91207 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -1947,10 +1947,6 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
>         if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
>                 goto send_now;
>
> -       /* If this packet won't get more data, do not wait. */
> -       if (TCP_SKB_CB(skb)->eor)
> -               goto send_now;
> -
>         win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor);
>         if (win_divisor) {
>                 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
> @@ -1999,7 +1995,8 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
>         }
>
>         /* If this packet won't get more data, do not wait. */
> -       if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
> +       if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) ||
> +           TCP_SKB_CB(skb)->eor)
>                 goto send_now;
>
>         return true;
> --
> 2.20.0.rc2.403.gdbc3b29805-goog
>

Re: [PATCH net-next] tcp: handle EOR and FIN conditions the same in tcp_tso_should_defer()

[David Miller]

From: Eric Dumazet <edumazet@google.com>
Date: Mon, 10 Dec 2018 06:10:02 -0800

> In commit f9bfe4e6a9d0 ("tcp: lack of available data can also cause
> TSO defer") we moved the test in tcp_tso_should_defer() for packets
> with a FIN flag, and we mentioned that the same would be done
> later for EOR flag.
> 
> Both flags should be handled at the same time, after all other
> heuristics have been considered. They both mean that no more bytes
> can be added to this skb by an application.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Applied, thanks Eric.