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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 <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2018-05-17 14:47:28 -07:00 committed by David S. Miller
parent 200d95f457
commit 6d82aa2420
5 changed files with 18 additions and 2 deletions
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7
Documentation/networking/ip-sysctl.txt
View File

@ -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

1
include/net/netns/ipv4.h
View File

@ -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;

7
net/ipv4/sysctl_net_ipv4.c
View File

@ -1151,6 +1151,13 @@ static struct ctl_table ipv4_net_table[] = {
.proc_handler = proc_dointvec_minmax,
.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,

4
net/ipv4/tcp_input.c
View File

@ -5113,13 +5113,13 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
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),

1
net/ipv4/tcp_ipv4.c
View File

@ -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;