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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>
This commit is contained in:
Ben Hutchings 2012-07-30 16:11:42 +00:00 committed by David S. Miller
parent 7e6d06f0de
commit 1485348d24
5 changed files with 20 additions and 11 deletions
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2
include/net/sock.h
View File

@ -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;

1
net/core/sock.c
View File

@ -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;
}
}
}

4
net/ipv4/tcp.c
View File

@ -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;
}
}

3
net/ipv4/tcp_cong.c
View File

@ -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);
}

21
net/ipv4/tcp_output.c
View File

@ -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)))