path: root/net/ipv4/tcp_ipv4.c
diff options
authorEric Dumazet <edumazet@google.com>2017-05-16 14:00:14 -0700
committerDavid S. Miller <davem@davemloft.net>2017-05-17 16:06:01 -0400
commit9a568de4818dea9a05af141046bd3e589245ab83 (patch)
tree6f1502edf55ecb7205660d62bd683ebcf912cfea /net/ipv4/tcp_ipv4.c
parenttcp: replace misc tcp_time_stamp to tcp_jiffies32 (diff)
tcp: switch TCP TS option (RFC 7323) to 1ms clock
TCP Timestamps option is defined in RFC 7323 Traditionally on linux, it has been tied to the internal 'jiffies' variable, because it had been a cheap and good enough generator. For TCP flows on the Internet, 1 ms resolution would be much better than 4ms or 10ms (HZ=250 or HZ=100 respectively) For TCP flows in the DC, Google has used usec resolution for more than two years with great success [1] Receive size autotuning (DRS) is indeed more precise and converges faster to optimal window size. This patch converts tp->tcp_mstamp to a plain u64 value storing a 1 usec TCP clock. This choice will allow us to upstream the 1 usec TS option as discussed in IETF 97. [1] https://www.ietf.org/proceedings/97/slides/slides-97-tcpm-tcp-options-for-low-latency-00.pdf Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_ipv4.c')
1 files changed, 9 insertions, 8 deletions
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index d8fe25db79f2..191b2f78b19d 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -376,8 +376,9 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
struct sock *sk;
struct sk_buff *skb;
struct request_sock *fastopen;
- __u32 seq, snd_una;
- __u32 remaining;
+ u32 seq, snd_una;
+ s32 remaining;
+ u32 delta_us;
int err;
struct net *net = dev_net(icmp_skb->dev);
@@ -483,12 +484,12 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
skb = tcp_write_queue_head(sk);
- skb_mstamp_get(&tp->tcp_mstamp);
+ tcp_mstamp_refresh(tp);
+ delta_us = (u32)(tp->tcp_mstamp - skb->skb_mstamp);
remaining = icsk->icsk_rto -
- min(icsk->icsk_rto,
- tcp_time_stamp - tcp_skb_timestamp(skb));
+ usecs_to_jiffies(delta_us);
- if (remaining) {
+ if (remaining > 0) {
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
remaining, TCP_RTO_MAX);
} else {
@@ -812,7 +813,7 @@ static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb)
tcp_v4_send_ack(sk, skb,
tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt,
tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale,
- tcp_time_stamp + tcptw->tw_ts_offset,
+ tcp_time_stamp_raw() + tcptw->tw_ts_offset,
@@ -840,7 +841,7 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
tcp_v4_send_ack(sk, skb, seq,
req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,
- tcp_time_stamp + tcp_rsk(req)->ts_off,
+ tcp_time_stamp_raw() + tcp_rsk(req)->ts_off,
tcp_md5_do_lookup(sk, (union tcp_md5_addr *)&ip_hdr(skb)->daddr,