From 6d82aa242092d73c6d2e210cfaf0ebfbe6de1ccf Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 17 May 2018 14:47:28 -0700 Subject: [PATCH] tcp: add tcp_comp_sack_delay_ns sysctl This per netns sysctl allows for TCP SACK compression fine-tuning. Its default value is 1,000,000, or 1 ms to meet TSO autosizing period. Signed-off-by: Eric Dumazet Acked-by: Neal Cardwell Signed-off-by: David S. Miller --- Documentation/networking/ip-sysctl.txt | 7 +++++++ include/net/netns/ipv4.h | 1 + net/ipv4/sysctl_net_ipv4.c | 7 +++++++ net/ipv4/tcp_input.c | 4 ++-- net/ipv4/tcp_ipv4.c | 1 + 5 files changed, 18 insertions(+), 2 deletions(-) diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index ea304a2..7ba9529 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -525,6 +525,13 @@ tcp_rmem - vector of 3 INTEGERs: min, default, max tcp_sack - BOOLEAN Enable select acknowledgments (SACKS). +tcp_comp_sack_delay_ns - LONG INTEGER + TCP tries to reduce number of SACK sent, using a timer + based on 5% of SRTT, capped by this sysctl, in nano seconds. + The default is 1ms, based on TSO autosizing period. + + Default : 1,000,000 ns (1 ms) + tcp_slow_start_after_idle - BOOLEAN If set, provide RFC2861 behavior and time out the congestion window after an idle period. An idle period is defined at diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h index 8491bc9..9273182 100644 --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -160,6 +160,7 @@ struct netns_ipv4 { int sysctl_tcp_pacing_ca_ratio; int sysctl_tcp_wmem[3]; int sysctl_tcp_rmem[3]; + unsigned long sysctl_tcp_comp_sack_delay_ns; struct inet_timewait_death_row tcp_death_row; int sysctl_max_syn_backlog; int sysctl_tcp_fastopen; diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 4b195ba..11fbfdc 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -1152,6 +1152,13 @@ static struct ctl_table ipv4_net_table[] = { .extra1 = &one, }, { + .procname = "tcp_comp_sack_delay_ns", + .data = &init_net.ipv4.sysctl_tcp_comp_sack_delay_ns, + .maxlen = sizeof(unsigned long), + .mode = 0644, + .proc_handler = proc_doulongvec_minmax, + }, + { .procname = "udp_rmem_min", .data = &init_net.ipv4.sysctl_udp_rmem_min, .maxlen = sizeof(init_net.ipv4.sysctl_udp_rmem_min), diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index cc2ac53..6a1dae38 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5113,13 +5113,13 @@ send_now: if (hrtimer_is_queued(&tp->compressed_ack_timer)) return; - /* compress ack timer : 5 % of rtt, but no more than 1 ms */ + /* compress ack timer : 5 % of rtt, but no more than tcp_comp_sack_delay_ns */ rtt = tp->rcv_rtt_est.rtt_us; if (tp->srtt_us && tp->srtt_us < rtt) rtt = tp->srtt_us; - delay = min_t(unsigned long, NSEC_PER_MSEC, + delay = min_t(unsigned long, sock_net(sk)->ipv4.sysctl_tcp_comp_sack_delay_ns, rtt * (NSEC_PER_USEC >> 3)/20); sock_hold(sk); hrtimer_start(&tp->compressed_ack_timer, ns_to_ktime(delay), diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index caf23de..a3f4647 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -2572,6 +2572,7 @@ static int __net_init tcp_sk_init(struct net *net) init_net.ipv4.sysctl_tcp_wmem, sizeof(init_net.ipv4.sysctl_tcp_wmem)); } + net->ipv4.sysctl_tcp_comp_sack_delay_ns = NSEC_PER_MSEC; net->ipv4.sysctl_tcp_fastopen = TFO_CLIENT_ENABLE; spin_lock_init(&net->ipv4.tcp_fastopen_ctx_lock); net->ipv4.sysctl_tcp_fastopen_blackhole_timeout = 60 * 60; -- 2.7.4