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authorFlorin Coras <fcoras@cisco.com>2018-11-13 00:03:43 -0800
committerDave Barach <openvpp@barachs.net>2018-11-13 18:16:36 +0000
commit6ebd4398ae3dabb19653d9dd3919b453dd17454b (patch)
tree70f0ec6a52c2efc574555ca7852aa560ed1960ff
parentaa01abb2b732abfb44559d25c9a11adfed57ac8b (diff)
tcp: cubic improvements
- avoid cwnd excessive increments on threshold changes - fix K computation when fastconvergence is on Change-Id: I99c36abc879e63aecc0617f7aed5a2f68430ba71 Signed-off-by: Florin Coras <fcoras@cisco.com>
-rw-r--r--src/vnet/tcp/tcp_cubic.c34
1 files changed, 25 insertions, 9 deletions
diff --git a/src/vnet/tcp/tcp_cubic.c b/src/vnet/tcp/tcp_cubic.c
index 55bbcca3497..717c54b146a 100644
--- a/src/vnet/tcp/tcp_cubic.c
+++ b/src/vnet/tcp/tcp_cubic.c
@@ -69,10 +69,12 @@ W_cubic (cubic_data_t * cd, f64 t)
* RFC 8312 Eq. 2
*/
static inline f64
-K_cubic (cubic_data_t * cd)
+K_cubic (cubic_data_t * cd, u32 wnd)
{
- /* K = cubic_root(W_max*(1-beta_cubic)/C) */
- return pow (cd->w_max * (1 - beta_cubic) / cubic_c, 1 / 3.0);
+ /* K = cubic_root(W_max*(1-beta_cubic)/C)
+ * Because the current window may be less than W_max * beta_cubic because
+ * of fast convergence, we pass it as parameter */
+ return pow ((f64) (cd->w_max - wnd) / cubic_c, 1 / 3.0);
}
/**
@@ -108,8 +110,23 @@ cubic_recovered (tcp_connection_t * tc)
{
cubic_data_t *cd = (cubic_data_t *) tcp_cc_data (tc);
cd->t_start = cubic_time (tc->c_thread_index);
- cd->K = K_cubic (cd);
tc->cwnd = tc->ssthresh;
+ cd->K = K_cubic (cd, tc->cwnd / tc->snd_mss);
+}
+
+static void
+cubic_cwnd_accumulate (tcp_connection_t * tc, u32 thresh, u32 bytes_acked)
+{
+ /* We just updated the threshold and don't know how large the previous
+ * one was. Still, optimistically increase cwnd by one segment and
+ * clear the accumulated bytes. */
+ if (tc->cwnd_acc_bytes > thresh)
+ {
+ tc->cwnd += tc->snd_mss;
+ tc->cwnd_acc_bytes = 0;
+ }
+
+ tcp_cwnd_accumulate (tc, thresh, tc->bytes_acked);
}
static void
@@ -137,7 +154,7 @@ cubic_rcv_ack (tcp_connection_t * tc)
w_aimd = (u64) W_est (cd, t, rtt_sec) * tc->snd_mss;
if (w_cubic < w_aimd)
{
- tcp_cwnd_accumulate (tc, tc->cwnd, tc->bytes_acked);
+ cubic_cwnd_accumulate (tc, tc->cwnd, tc->bytes_acked);
}
else
{
@@ -155,16 +172,15 @@ cubic_rcv_ack (tcp_connection_t * tc)
*/
thresh = (tc->snd_mss * tc->cwnd) / (w_cubic - tc->cwnd);
- /* Make sure we don't increase cwnd more often than every
- * 2 segments */
- thresh = clib_max (thresh, 2 * tc->snd_mss);
+ /* Make sure we don't increase cwnd more often than every segment */
+ thresh = clib_max (thresh, tc->snd_mss);
}
else
{
/* Practically we can't increment so just inflate threshold */
thresh = 50 * tc->cwnd;
}
- tcp_cwnd_accumulate (tc, thresh, tc->bytes_acked);
+ cubic_cwnd_accumulate (tc, thresh, tc->bytes_acked);
}
}