diff options
author | Eric Dumazet <edumazet@google.com> | 2017-04-25 10:15:41 -0700 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2017-04-26 14:44:39 -0400 |
commit | 645f4c6f2ebd040688cc2a5f626ffc909e66ccf2 (patch) | |
tree | 7ceebdc356adf410a9d78bd51d7e200697d19658 /net/ipv4/tcp.c | |
parent | a6db50b81e3f20b2b692bbddd35d9484057eae9d (diff) |
tcp: switch rcv_rtt_est and rcvq_space to high resolution timestamps
Some devices or distributions use HZ=100 or HZ=250
TCP receive buffer autotuning has poor behavior caused by this choice.
Since autotuning happens after 4 ms or 10 ms, short distance flows
get their receive buffer tuned to a very high value, but after an initial
period where it was frozen to (too small) initial value.
With tp->tcp_mstamp introduction, we can switch to high resolution
timestamps almost for free (at the expense of 8 additional bytes per
TCP structure)
Note that some TCP stacks use usec TCP timestamps where this
patch makes even more sense : Many TCP flows have < 500 usec RTT.
Hopefully this finer TS option can be standardized soon.
Tested:
HZ=100 kernel
./netperf -H lpaa24 -t TCP_RR -l 1000 -- -r 10000,10000 &
Peer without patch :
lpaa24:~# ss -tmi dst lpaa23
...
skmem:(r0,rb8388608,...)
rcv_rtt:10 rcv_space:3210000 minrtt:0.017
Peer with the patch :
lpaa23:~# ss -tmi dst lpaa24
...
skmem:(r0,rb428800,...)
rcv_rtt:0.069 rcv_space:30000 minrtt:0.017
We can see saner RCVBUF, and more precise rcv_rtt information.
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>
Diffstat (limited to 'net/ipv4/tcp.c')
-rw-r--r-- | net/ipv4/tcp.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index efc976ae66ae..059dad7deefe 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2853,7 +2853,7 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info) info->tcpi_snd_ssthresh = tp->snd_ssthresh; info->tcpi_advmss = tp->advmss; - info->tcpi_rcv_rtt = jiffies_to_usecs(tp->rcv_rtt_est.rtt)>>3; + info->tcpi_rcv_rtt = tp->rcv_rtt_est.rtt_us >> 3; info->tcpi_rcv_space = tp->rcvq_space.space; info->tcpi_total_retrans = tp->total_retrans; |