Files
linux/include/linux
Eric Dumazet 645f4c6f2e 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>
2017-04-26 14:44:39 -04:00
..
2017-03-07 14:30:38 +01:00
2017-01-24 12:37:43 -08:00
2017-04-17 11:08:31 -04:00
2016-12-22 22:58:37 -05:00
2017-02-10 15:52:24 -05:00
2017-01-25 13:17:47 -05:00
2017-04-11 14:38:43 -04:00
2016-12-08 16:37:33 -08:00
2017-02-24 17:46:55 -08:00
2017-02-04 00:47:59 +01:00
2016-12-05 19:01:16 -05:00
2017-02-27 10:07:47 -08:00
2016-12-05 19:01:16 -05:00
2016-12-25 17:21:22 +01:00
2017-03-22 00:18:22 -07:00
2017-02-11 20:59:41 -05:00
2017-03-22 16:16:17 +01:00
2017-01-05 15:01:55 -06:00
2017-02-01 09:13:45 +01:00
2016-12-12 18:55:06 -08:00
2016-12-25 17:21:23 +01:00
2017-02-24 17:46:57 -08:00
2016-12-06 11:05:46 +01:00
2017-04-24 14:30:46 -04:00
2017-01-12 16:48:26 -05:00
2016-12-12 18:55:07 -08:00
2016-12-06 10:17:03 +02:00
2017-04-11 11:16:03 -04:00
2017-04-24 12:40:24 -04:00
2017-02-13 21:44:09 -05:00
2017-02-27 18:43:46 -08:00
2017-04-14 10:05:36 +02:00
2017-01-09 16:07:38 -05:00
2017-03-22 12:15:15 -07:00
2016-12-25 17:21:22 +01:00
2017-01-10 18:31:55 -08:00
2017-02-03 10:17:02 +01:00
2017-02-10 16:34:17 +00:00
2016-12-12 18:55:08 -08:00
2017-01-11 09:21:41 +01:00
2017-02-02 15:22:18 -05:00