To allow congestion control modules to use the default TSO auto-sizing
algorithm as one of the ingredients in their own decision about TSO sizing:

1) Export tcp_tso_autosize() so that CC modules can use it.

2) Change tcp_tso_autosize() to allow callers to specify a minimum
   number of segments per TSO skb, in case the congestion control
   module has a different notion of the best floor for TSO skbs for
   the connection right now. For very low-rate paths or policed
   connections it can be appropriate to use smaller TSO skbs.

Signed-off-by: Van Jacobson <>
Signed-off-by: Neal Cardwell <>
Signed-off-by: Yuchung Cheng <>
Signed-off-by: Nandita Dukkipati <>
Signed-off-by: Eric Dumazet <>
Signed-off-by: Soheil Hassas Yeganeh <>
 include/net/tcp.h     | 2 ++
 net/ipv4/tcp_output.c | 9 ++++++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4d85cd7..8805c65 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -533,6 +533,8 @@ __u32 cookie_v6_init_sequence(const struct sk_buff *skb, 
__u16 *mss);
 /* tcp_output.c */
+u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
+                    int min_tso_segs);
 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
                               int nonagle);
 bool tcp_may_send_now(struct sock *sk);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 0137956..0bf3d48 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1549,7 +1549,8 @@ static bool tcp_nagle_check(bool partial, const struct 
tcp_sock *tp,
 /* Return how many segs we'd like on a TSO packet,
  * to send one TSO packet per ms
-static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now)
+u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
+                    int min_tso_segs)
        u32 bytes, segs;
@@ -1561,10 +1562,11 @@ static u32 tcp_tso_autosize(const struct sock *sk, 
unsigned int mss_now)
         * This preserves ACK clocking and is consistent
         * with tcp_tso_should_defer() heuristic.
-       segs = max_t(u32, bytes / mss_now, sysctl_tcp_min_tso_segs);
+       segs = max_t(u32, bytes / mss_now, min_tso_segs);
        return min_t(u32, segs, sk->sk_gso_max_segs);
 /* Return the number of segments we want in the skb we are transmitting.
  * See if congestion control module wants to decide; otherwise, autosize.
@@ -1574,7 +1576,8 @@ static u32 tcp_tso_segs(struct sock *sk, unsigned int 
        const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
        u32 tso_segs = ca_ops->tso_segs_goal ? ca_ops->tso_segs_goal(sk) : 0;
-       return tso_segs ? : tcp_tso_autosize(sk, mss_now);
+       return tso_segs ? :
+               tcp_tso_autosize(sk, mss_now, sysctl_tcp_min_tso_segs);
 /* Returns the portion of skb which can be sent right away */

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