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| author | Eric Dumazet <edumazet@google.com> | 2017-05-16 14:00:14 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-05-17 16:06:01 -0400 |
| commit | 9a568de4818dea9a05af141046bd3e589245ab83 (patch) | |
| tree | 6f1502edf55ecb7205660d62bd683ebcf912cfea /net/ipv4/tcp.c | |
| parent | ac9517fcf310327fa3e3b0d8366e4b11236b1b4b (diff) | |
| download | op-kernel-dev-9a568de4818dea9a05af141046bd3e589245ab83.zip op-kernel-dev-9a568de4818dea9a05af141046bd3e589245ab83.tar.gz | |
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.c')
| -rw-r--r-- | net/ipv4/tcp.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 8500548..b5d1848 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2706,7 +2706,7 @@ static int do_tcp_setsockopt(struct sock *sk, int level, if (!tp->repair) err = -EPERM; else - tp->tsoffset = val - tcp_time_stamp; + tp->tsoffset = val - tcp_time_stamp_raw(); break; case TCP_REPAIR_WINDOW: err = tcp_repair_set_window(tp, optval, optlen); @@ -3072,7 +3072,7 @@ static int do_tcp_getsockopt(struct sock *sk, int level, break; case TCP_TIMESTAMP: - val = tcp_time_stamp + tp->tsoffset; + val = tcp_time_stamp_raw() + tp->tsoffset; break; case TCP_NOTSENT_LOWAT: val = tp->notsent_lowat; |
