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tcp: add hrtimer slack to sack compression

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Add a sysctl to control hrtimer slack, default of 100 usec.

This gives the opportunity to reduce system overhead,
and help very short RTT flows.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@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
2020-04-30 10:35:43 -07:00
committed by David S. Miller
parent ccd0628fca
commit a70437cc09
5 changed files with 20 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
net/ipv4/sysctl_net_ipv4.c
View File

@@ -1329,6 +1329,13 @@ static struct ctl_table ipv4_net_table[] = {
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
},
{
.procname = "tcp_comp_sack_slack_ns",
.data = &init_net.ipv4.sysctl_tcp_comp_sack_slack_ns,
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
},
{
.procname = "tcp_comp_sack_nr",
.data = &init_net.ipv4.sysctl_tcp_comp_sack_nr,

5
net/ipv4/tcp_input.c
View File

@@ -5324,8 +5324,9 @@ send_now:
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),
HRTIMER_MODE_REL_PINNED_SOFT);
hrtimer_start_range_ns(&tp->compressed_ack_timer, ns_to_ktime(delay),
sock_net(sk)->ipv4.sysctl_tcp_comp_sack_slack_ns,
HRTIMER_MODE_REL_PINNED_SOFT);
}
static inline void tcp_ack_snd_check(struct sock *sk)

1
net/ipv4/tcp_ipv4.c
View File

@@ -2780,6 +2780,7 @@ static int __net_init tcp_sk_init(struct net *net)
sizeof(init_net.ipv4.sysctl_tcp_wmem));
}
net->ipv4.sysctl_tcp_comp_sack_delay_ns = NSEC_PER_MSEC;
net->ipv4.sysctl_tcp_comp_sack_slack_ns = 100 * NSEC_PER_USEC;
net->ipv4.sysctl_tcp_comp_sack_nr = 44;
net->ipv4.sysctl_tcp_fastopen = TFO_CLIENT_ENABLE;
spin_lock_init(&net->ipv4.tcp_fastopen_ctx_lock);