tcp: fast retransmit improvements
Patch is too large to be ported to 18.10 just days before release.
- handle fast retransmits outside of established node and limit the
retransmit burst size to avoid tx losses and worsening congestion.
- in the absance of a tx pacer, use slow start after fast retransmit
exists
- add fast retransmit heuristic that re-retries sending the first
segment if everything else fails
- fine tuning
Change-Id: I84a2ab8fbba8b97f1d2b26584dc11a1e2c33c8d2
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vnet/tcp/tcp.c b/src/vnet/tcp/tcp.c
index e32b5c4..cb05b8c 100644
--- a/src/vnet/tcp/tcp.c
+++ b/src/vnet/tcp/tcp.c
@@ -950,7 +950,8 @@
hole = scoreboard_first_hole (sb);
if (hole)
- s = format (s, "\n head %u tail %u holes:\n", sb->head, sb->tail);
+ s = format (s, "\n head %u tail %u %u holes:\n", sb->head, sb->tail,
+ pool_elts (sb->holes));
while (hole)
{
@@ -1027,7 +1028,7 @@
{
int snd_space, snt_limited;
- if (PREDICT_TRUE (tcp_in_cong_recovery (tc) == 0))
+ if (PREDICT_TRUE (!tcp_in_fastrecovery (tc)))
{
snd_space = tcp_available_output_snd_space (tc);
@@ -1047,16 +1048,6 @@
return tcp_round_snd_space (tc, snd_space);
}
- if (tcp_in_recovery (tc))
- {
- tc->snd_nxt = tc->snd_una_max;
- snd_space = tcp_available_snd_wnd (tc) - tc->snd_rxt_bytes
- - (tc->snd_una_max - tc->snd_congestion);
- if (snd_space <= 0 || (tc->snd_una_max - tc->snd_una) >= tc->snd_wnd)
- return 0;
- return tcp_round_snd_space (tc, snd_space);
- }
-
/* RFC 5681: When previously unsent data is available and the new value of
* cwnd and the receiver's advertised window allow, a TCP SHOULD send 1*SMSS
* bytes of previously unsent data. */
@@ -1103,6 +1094,7 @@
tw_timer_expire_timers_16t_2w_512sl (&tcp_main.
wrk_ctx[thread_index].timer_wheel,
now);
+ tcp_do_fastretransmits (thread_index);
tcp_flush_frames_to_output (thread_index);
}