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authorFlorin Coras <fcoras@cisco.com>2022-01-09 18:18:10 -0800
committerFlorin Coras <florin.coras@gmail.com>2022-01-10 03:12:46 +0000
commit9bd71be3eef15fa7a037debf9713f7d8db62935f (patch)
treec0581e7c4907b213be82bd0bb0f0d296fc7e6d29
parent93dd58c8fb020870c770c2a4aa55dcc288fa2035 (diff)
session: deschedule sessions with no data to send
This ensures the scheduler always tracks sessions that are descheduled, i.e., do not have events in the old io events list. When app retries to send, clear descheduled flag and potentially the pacer. Consequently, transports no longer need to reset the pacer when sessions are rescheduled after a long app tx pause. This also fixes a tcp bug whereby the pacer was reset too often when snd_una was equal to snd_nxt as there was no way to distinguish betwen app tx breaks and congestion. Type: improvement Signed-off-by: Florin Coras <fcoras@cisco.com> Change-Id: Id3cc6c98cd76299e15030e504380dcf3c04c5189
-rw-r--r--src/vnet/session/session_node.c15
-rw-r--r--src/vnet/session/transport.h13
-rw-r--r--src/vnet/tcp/tcp_output.c1
3 files changed, 26 insertions, 3 deletions
diff --git a/src/vnet/session/session_node.c b/src/vnet/session/session_node.c
index 1d7ebf9f11a..bebabd3d68e 100644
--- a/src/vnet/session/session_node.c
+++ b/src/vnet/session/session_node.c
@@ -1188,8 +1188,14 @@ session_tx_maybe_reschedule (session_worker_t * wrk,
svm_fifo_unset_event (s->tx_fifo);
if (svm_fifo_max_dequeue_cons (s->tx_fifo) > ctx->sp.tx_offset)
- if (svm_fifo_set_event (s->tx_fifo))
- session_evt_add_head_old (wrk, elt);
+ {
+ if (svm_fifo_set_event (s->tx_fifo))
+ session_evt_add_head_old (wrk, elt);
+ }
+ else
+ {
+ transport_connection_deschedule (ctx->tc);
+ }
}
always_inline int
@@ -1246,6 +1252,11 @@ session_tx_fifo_read_and_snd_i (session_worker_t * wrk,
}
}
+ /* Connection previously descheduled because it had no data to send.
+ * Clear descheduled flag and reset pacer if in use */
+ if (transport_connection_is_descheduled (ctx->tc))
+ transport_connection_clear_descheduled (ctx->tc);
+
transport_connection_snd_params (ctx->tc, &ctx->sp);
if (!ctx->sp.snd_space)
diff --git a/src/vnet/session/transport.h b/src/vnet/session/transport.h
index 2cfec06ec94..549f17957cc 100644
--- a/src/vnet/session/transport.h
+++ b/src/vnet/session/transport.h
@@ -327,6 +327,19 @@ transport_connection_is_tx_paced (transport_connection_t * tc)
return (tc->flags & TRANSPORT_CONNECTION_F_IS_TX_PACED);
}
+/**
+ * Clear descheduled flag and update pacer if needed
+ *
+ * To add session to scheduler use @ref transport_connection_reschedule
+ */
+always_inline void
+transport_connection_clear_descheduled (transport_connection_t *tc)
+{
+ tc->flags &= ~TRANSPORT_CONNECTION_F_DESCHED;
+ if (transport_connection_is_tx_paced (tc))
+ transport_connection_tx_pacer_reset_bucket (tc, 0 /* bucket */);
+}
+
u8 *format_transport_pacer (u8 * s, va_list * args);
/**
diff --git a/src/vnet/tcp/tcp_output.c b/src/vnet/tcp/tcp_output.c
index 5647b8f6737..55fa6d1b5d8 100644
--- a/src/vnet/tcp/tcp_output.c
+++ b/src/vnet/tcp/tcp_output.c
@@ -321,7 +321,6 @@ tcp_update_burst_snd_vars (tcp_connection_t * tc)
if (tc->snd_una == tc->snd_nxt)
{
tcp_cc_event (tc, TCP_CC_EVT_START_TX);
- tcp_connection_tx_pacer_reset (tc, tc->cwnd, TRANSPORT_PACER_MIN_BURST);
}
if (tc->flags & TCP_CONN_PSH_PENDING)