path: root/net/ipv4/tcp_input.c
diff options
authorYuchung Cheng <ycheng@google.com>2018-09-27 11:21:19 -0700
committerDavid S. Miller <davem@davemloft.net>2018-09-29 11:22:22 -0700
commita337531b942bd8a03e7052444d7e36972aac2d92 (patch)
tree32b97fbbf43d08936e0fbe9227158b0ea6508d36 /net/ipv4/tcp_input.c
parenthns3: Another build fix. (diff)
tcp: up initial rmem to 128KB and SYN rwin to around 64KB
Previously TCP initial receive buffer is ~87KB by default and the initial receive window is ~29KB (20 MSS). This patch changes the two numbers to 128KB and ~64KB (rounding down to the multiples of MSS) respectively. The patch also simplifies the calculations s.t. the two numbers are directly controlled by sysctl tcp_rmem[1]: 1) Initial receiver buffer budget (sk_rcvbuf): while this should be configured via sysctl tcp_rmem[1], previously tcp_fixup_rcvbuf() always override and set a larger size when a new connection establishes. 2) Initial receive window in SYN: previously it is set to 20 packets if MSS <= 1460. The number 20 was based on the initial congestion window of 10: the receiver needs twice amount to avoid being limited by the receive window upon out-of-order delivery in the first window burst. But since this only applies if the receiving MSS <= 1460, connection using large MTU (e.g. to utilize receiver zero-copy) may be limited by the receive window. With this patch TCP memory configuration is more straight-forward and more properly sized to modern high-speed networks by default. Several popular stacks have been announcing 64KB rwin in SYNs as well. Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Wei Wang <weiwan@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_input.c')
1 files changed, 2 insertions, 23 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d703a0b3b6a2..7a59f6a96212 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -426,26 +426,7 @@ static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb)
-/* 3. Tuning rcvbuf, when connection enters established state. */
-static void tcp_fixup_rcvbuf(struct sock *sk)
- u32 mss = tcp_sk(sk)->advmss;
- int rcvmem;
- rcvmem = 2 * SKB_TRUESIZE(mss + MAX_TCP_HEADER) *
- tcp_default_init_rwnd(mss);
- /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
- * Allow enough cushion so that sender is not limited by our window
- */
- if (sock_net(sk)->ipv4.sysctl_tcp_moderate_rcvbuf)
- rcvmem <<= 2;
- if (sk->sk_rcvbuf < rcvmem)
- sk->sk_rcvbuf = min(rcvmem, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
-/* 4. Try to fixup all. It is made immediately after connection enters
+/* 3. Try to fixup all. It is made immediately after connection enters
* established state.
void tcp_init_buffer_space(struct sock *sk)
@@ -454,8 +435,6 @@ void tcp_init_buffer_space(struct sock *sk)
struct tcp_sock *tp = tcp_sk(sk);
int maxwin;
- if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
- tcp_fixup_rcvbuf(sk);
if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
@@ -485,7 +464,7 @@ void tcp_init_buffer_space(struct sock *sk)
tp->snd_cwnd_stamp = tcp_jiffies32;
-/* 5. Recalculate window clamp after socket hit its memory bounds. */
+/* 4. Recalculate window clamp after socket hit its memory bounds. */
static void tcp_clamp_window(struct sock *sk)
struct tcp_sock *tp = tcp_sk(sk);