tcp_bbr: cut pacing rate only if filled pipe
authorNeal Cardwell <ncardwell@google.com>
Fri, 14 Jul 2017 21:49:21 +0000 (17:49 -0400)
committerDavid S. Miller <davem@davemloft.net>
Sat, 15 Jul 2017 21:43:29 +0000 (14:43 -0700)
commit4aea287e90dd61a48268ff2994b56f9799441b62
tree2e1663c9bfcdc6a5a5895272216c26ec1811fac5
parent8b97ac5bda17cfaa257bcab6180af0f43a2e87e0
tcp_bbr: cut pacing rate only if filled pipe

In bbr_set_pacing_rate(), which decides whether to cut the pacing
rate, there was some code that considered exiting STARTUP to be
equivalent to the notion of filling the pipe (i.e.,
bbr_full_bw_reached()). Specifically, as the code was structured,
exiting STARTUP and going into PROBE_RTT could cause us to cut the
pacing rate down to something silly and low, based on whatever
bandwidth samples we've had so far, when it's possible that all of
them have been small app-limited bandwidth samples that are not
representative of the bandwidth available in the path. (The code was
correct at the time it was written, but the state machine changed
without this spot being adjusted correspondingly.)

Fixes: 0f8782ea1497 ("tcp_bbr: add BBR congestion control")
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/ipv4/tcp_bbr.c