forked from luck/tmp_suning_uos_patched
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>
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parent
3ff6cde846
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a337531b94
net/ipv4
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@ -3896,8 +3896,8 @@ void __init tcp_init(void)
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init_net.ipv4.sysctl_tcp_wmem[2] = max(64*1024, max_wshare);
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init_net.ipv4.sysctl_tcp_rmem[0] = SK_MEM_QUANTUM;
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init_net.ipv4.sysctl_tcp_rmem[1] = 87380;
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init_net.ipv4.sysctl_tcp_rmem[2] = max(87380, max_rshare);
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init_net.ipv4.sysctl_tcp_rmem[1] = 131072;
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init_net.ipv4.sysctl_tcp_rmem[2] = max(131072, max_rshare);
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pr_info("Hash tables configured (established %u bind %u)\n",
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tcp_hashinfo.ehash_mask + 1, tcp_hashinfo.bhash_size);
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@ -426,26 +426,7 @@ static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb)
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}
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}
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/* 3. Tuning rcvbuf, when connection enters established state. */
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static void tcp_fixup_rcvbuf(struct sock *sk)
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{
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u32 mss = tcp_sk(sk)->advmss;
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int rcvmem;
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rcvmem = 2 * SKB_TRUESIZE(mss + MAX_TCP_HEADER) *
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tcp_default_init_rwnd(mss);
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/* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
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* Allow enough cushion so that sender is not limited by our window
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*/
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if (sock_net(sk)->ipv4.sysctl_tcp_moderate_rcvbuf)
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rcvmem <<= 2;
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if (sk->sk_rcvbuf < rcvmem)
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sk->sk_rcvbuf = min(rcvmem, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
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}
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/* 4. Try to fixup all. It is made immediately after connection enters
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/* 3. Try to fixup all. It is made immediately after connection enters
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* established state.
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*/
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void tcp_init_buffer_space(struct sock *sk)
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@ -454,8 +435,6 @@ void tcp_init_buffer_space(struct sock *sk)
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struct tcp_sock *tp = tcp_sk(sk);
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int maxwin;
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if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
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tcp_fixup_rcvbuf(sk);
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if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
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tcp_sndbuf_expand(sk);
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@ -485,7 +464,7 @@ void tcp_init_buffer_space(struct sock *sk)
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tp->snd_cwnd_stamp = tcp_jiffies32;
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}
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/* 5. Recalculate window clamp after socket hit its memory bounds. */
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/* 4. Recalculate window clamp after socket hit its memory bounds. */
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static void tcp_clamp_window(struct sock *sk)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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@ -195,21 +195,6 @@ static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts,
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inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
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}
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u32 tcp_default_init_rwnd(u32 mss)
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{
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/* Initial receive window should be twice of TCP_INIT_CWND to
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* enable proper sending of new unsent data during fast recovery
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* (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
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* limit when mss is larger than 1460.
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*/
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u32 init_rwnd = TCP_INIT_CWND * 2;
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if (mss > 1460)
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init_rwnd = max((1460 * init_rwnd) / mss, 2U);
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return init_rwnd;
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}
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/* Determine a window scaling and initial window to offer.
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* Based on the assumption that the given amount of space
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* will be offered. Store the results in the tp structure.
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@ -244,7 +229,10 @@ void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
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if (sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
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(*rcv_wnd) = min(space, MAX_TCP_WINDOW);
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else
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(*rcv_wnd) = space;
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(*rcv_wnd) = min_t(u32, space, U16_MAX);
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if (init_rcv_wnd)
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*rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
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(*rcv_wscale) = 0;
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if (wscale_ok) {
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@ -257,11 +245,6 @@ void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
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(*rcv_wscale)++;
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}
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}
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if (!init_rcv_wnd) /* Use default unless specified otherwise */
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init_rcv_wnd = tcp_default_init_rwnd(mss);
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*rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
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/* Set the clamp no higher than max representable value */
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(*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);
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}
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