diff options
| -rw-r--r-- | Documentation/networking/ip-sysctl.rst | 23 | ||||
| -rw-r--r-- | include/net/netns/ipv4.h | 3 | ||||
| -rw-r--r-- | net/ipv4/sysctl_net_ipv4.c | 7 | ||||
| -rw-r--r-- | net/ipv4/tcp_ipv4.c | 1 | ||||
| -rw-r--r-- | net/ipv4/tcp_output.c | 33 |
5 files changed, 54 insertions, 13 deletions
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index 2572eecc3e86..b0024aa7b051 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -878,6 +878,29 @@ tcp_min_tso_segs - INTEGER Default: 2 +tcp_tso_rtt_log - INTEGER + Adjustment of TSO packet sizes based on min_rtt + + Starting from linux-5.18, TCP autosizing can be tweaked + for flows having small RTT. + + Old autosizing was splitting the pacing budget to send 1024 TSO + per second. + + tso_packet_size = sk->sk_pacing_rate / 1024; + + With the new mechanism, we increase this TSO sizing using: + + distance = min_rtt_usec / (2^tcp_tso_rtt_log) + tso_packet_size += gso_max_size >> distance; + + This means that flows between very close hosts can use bigger + TSO packets, reducing their cpu costs. + + If you want to use the old autosizing, set this sysctl to 0. + + Default: 9 (2^9 = 512 usec) + tcp_pacing_ss_ratio - INTEGER sk->sk_pacing_rate is set by TCP stack using a ratio applied to current rate. (current_rate = cwnd * mss / srtt) diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h index f0687867b5cd..ce0cc4e8d8c7 100644 --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -127,6 +127,7 @@ struct netns_ipv4 { u8 sysctl_tcp_synack_retries; u8 sysctl_tcp_syncookies; u8 sysctl_tcp_migrate_req; + u8 sysctl_tcp_comp_sack_nr; int sysctl_tcp_reordering; u8 sysctl_tcp_retries1; u8 sysctl_tcp_retries2; @@ -160,9 +161,9 @@ struct netns_ipv4 { int sysctl_tcp_challenge_ack_limit; int sysctl_tcp_min_rtt_wlen; u8 sysctl_tcp_min_tso_segs; + u8 sysctl_tcp_tso_rtt_log; u8 sysctl_tcp_autocorking; u8 sysctl_tcp_reflect_tos; - u8 sysctl_tcp_comp_sack_nr; int sysctl_tcp_invalid_ratelimit; int sysctl_tcp_pacing_ss_ratio; int sysctl_tcp_pacing_ca_ratio; diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 1cae27b5dcd8..ad80d180b60b 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -1272,6 +1272,13 @@ static struct ctl_table ipv4_net_table[] = { .extra1 = SYSCTL_ONE, }, { + .procname = "tcp_tso_rtt_log", + .data = &init_net.ipv4.sysctl_tcp_tso_rtt_log, + .maxlen = sizeof(u8), + .mode = 0644, + .proc_handler = proc_dou8vec_minmax, + }, + { .procname = "tcp_min_rtt_wlen", .data = &init_net.ipv4.sysctl_tcp_min_rtt_wlen, .maxlen = sizeof(int), diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 81694a354110..f9cec624068d 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -3137,6 +3137,7 @@ static int __net_init tcp_sk_init(struct net *net) /* rfc5961 challenge ack rate limiting */ net->ipv4.sysctl_tcp_challenge_ack_limit = 1000; net->ipv4.sysctl_tcp_min_tso_segs = 2; + net->ipv4.sysctl_tcp_tso_rtt_log = 9; /* 2^9 = 512 usec */ net->ipv4.sysctl_tcp_min_rtt_wlen = 300; net->ipv4.sysctl_tcp_autocorking = 1; net->ipv4.sysctl_tcp_invalid_ratelimit = HZ/2; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 2319531267c6..81aaa7da3e8c 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1951,25 +1951,34 @@ 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 + * depending on current pacing rate, and how close the peer is. + * + * Rationale is: + * - For close peers, we rather send bigger packets to reduce + * cpu costs, because occasional losses will be repaired fast. + * - For long distance/rtt flows, we would like to get ACK clocking + * with 1 ACK per ms. + * + * Use min_rtt to help adapt TSO burst size, with smaller min_rtt resulting + * in bigger TSO bursts. We we cut the RTT-based allowance in half + * for every 2^9 usec (aka 512 us) of RTT, so that the RTT-based allowance + * is below 1500 bytes after 6 * ~500 usec = 3ms. */ static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now, int min_tso_segs) { - u32 bytes, segs; + unsigned long bytes; + u32 r; - bytes = min_t(unsigned long, - sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift), - sk->sk_gso_max_size); + bytes = sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift); - /* Goal is to send at least one packet per ms, - * not one big TSO packet every 100 ms. - * This preserves ACK clocking and is consistent - * with tcp_tso_should_defer() heuristic. - */ - segs = max_t(u32, bytes / mss_now, min_tso_segs); + r = tcp_min_rtt(tcp_sk(sk)) >> sock_net(sk)->ipv4.sysctl_tcp_tso_rtt_log; + if (r < BITS_PER_TYPE(sk->sk_gso_max_size)) + bytes += sk->sk_gso_max_size >> r; + + bytes = min_t(unsigned long, bytes, sk->sk_gso_max_size); - return segs; + return max_t(u32, bytes / mss_now, min_tso_segs); } /* Return the number of segments we want in the skb we are transmitting. |