tcp: Apply device TSO segment limit earlier

Cache the device gso_max_segs in sock::sk_gso_max_segs and use it to
limit the size of TSO skbs.  This avoids the need to fall back to
software GSO for local TCP senders.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/sock.h b/include/net/sock.h
index b3730239bf1828bd9fb618b8b8988b37832fe5c3..72132aef53fc61a721ce23c8fbc4fe17cb7a9699 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -218,6 +218,7 @@ struct cg_proto;
   *    @sk_route_nocaps: forbidden route capabilities (e.g NETIF_F_GSO_MASK)
   *    @sk_gso_type: GSO type (e.g. %SKB_GSO_TCPV4)
   *    @sk_gso_max_size: Maximum GSO segment size to build
+  *    @sk_gso_max_segs: Maximum number of GSO segments
   *    @sk_lingertime: %SO_LINGER l_linger setting
   *    @sk_backlog: always used with the per-socket spinlock held
   *    @sk_callback_lock: used with the callbacks in the end of this struct
@@ -338,6 +339,7 @@ struct sock {
        netdev_features_t       sk_route_nocaps;
        int                     sk_gso_type;
        unsigned int            sk_gso_max_size;
+       u16                     sk_gso_max_segs;
        int                     sk_rcvlowat;
        unsigned long           sk_lingertime;
        struct sk_buff_head     sk_error_queue;

diff --git a/net/core/sock.c b/net/core/sock.c
index 6b654b3ddfda2a9a03f77bc1d2a5476a2c25e9d4..8f67ced8d6a808689255435dd412df132138af65 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1458,6 +1458,7 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
                } else {
                        sk->sk_route_caps |= NETIF_F_SG | NETIF_F_HW_CSUM;
                        sk->sk_gso_max_size = dst->dev->gso_max_size;
+                       sk->sk_gso_max_segs = dst->dev->gso_max_segs;
                }
        }
 }

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e7e6eeae49c0123d392fa16c7687c333b30b79b8..2109ff4a1dafd489fbe0e2240075432df4517374 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -811,7 +811,9 @@ static unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now,
                           old_size_goal + mss_now > xmit_size_goal)) {
                        xmit_size_goal = old_size_goal;
                } else {
-                       tp->xmit_size_goal_segs = xmit_size_goal / mss_now;
+                       tp->xmit_size_goal_segs =
+                               min_t(u16, xmit_size_goal / mss_now,
+                                     sk->sk_gso_max_segs);
                        xmit_size_goal = tp->xmit_size_goal_segs * mss_now;
                }
        }

diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 4d4db16e336ea63c2b581079e5295a4a74924aab..1432cdb0644c2b16f893de842bcd3b9fdd3c5538 100644 (file)
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -291,7 +291,8 @@ bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight)
        left = tp->snd_cwnd - in_flight;
        if (sk_can_gso(sk) &&
            left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd &&
-           left * tp->mss_cache < sk->sk_gso_max_size)
+           left * tp->mss_cache < sk->sk_gso_max_size &&
+           left < sk->sk_gso_max_segs)
                return true;
        return left <= tcp_max_tso_deferred_mss(tp);
 }

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 3f1bcff0b10b5d2daa0307de4ff29f0ba6ddb5cc..a7b3ec9b6c3ee33a9bc8730c45f8f3d85b034196 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1522,21 +1522,21 @@ static void tcp_cwnd_validate(struct sock *sk)
  * when we would be allowed to send the split-due-to-Nagle skb fully.
  */
 static unsigned int tcp_mss_split_point(const struct sock *sk, const struct sk_buff *skb,
-                                       unsigned int mss_now, unsigned int cwnd)
+                                       unsigned int mss_now, unsigned int max_segs)
 {
        const struct tcp_sock *tp = tcp_sk(sk);
-       u32 needed, window, cwnd_len;
+       u32 needed, window, max_len;
 
        window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
-       cwnd_len = mss_now * cwnd;
+       max_len = mss_now * max_segs;
 
-       if (likely(cwnd_len <= window && skb != tcp_write_queue_tail(sk)))
-               return cwnd_len;
+       if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
+               return max_len;
 
        needed = min(skb->len, window);
 
-       if (cwnd_len <= needed)
-               return cwnd_len;
+       if (max_len <= needed)
+               return max_len;
 
        return needed - needed % mss_now;
 }
@@ -1765,7 +1765,8 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
        limit = min(send_win, cong_win);
 
        /* If a full-sized TSO skb can be sent, do it. */
-       if (limit >= sk->sk_gso_max_size)
+       if (limit >= min_t(unsigned int, sk->sk_gso_max_size,
+                          sk->sk_gso_max_segs * tp->mss_cache))
                goto send_now;
 
        /* Middle in queue won't get any more data, full sendable already? */
@@ -1999,7 +2000,9 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
                limit = mss_now;
                if (tso_segs > 1 && !tcp_urg_mode(tp))
                        limit = tcp_mss_split_point(sk, skb, mss_now,
-                                                   cwnd_quota);
+                                                   min_t(unsigned int,
+                                                         cwnd_quota,
+                                                         sk->sk_gso_max_segs));
 
                if (skb->len > limit &&
                    unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))