tcp: improve pacing after idle send periods
Rest pacer on ack reception if we haven't recently sent anything.
Type: feature
Change-Id: I820bacd81b65130052dfafbfcbe6ca4553069fbc
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vnet/session/session_node.c b/src/vnet/session/session_node.c
index 9e53718..f51b892 100644
--- a/src/vnet/session/session_node.c
+++ b/src/vnet/session/session_node.c
@@ -845,6 +845,7 @@
{
if (ctx->transport_vft->flush_data)
ctx->transport_vft->flush_data (ctx->tc);
+ e->event_type = SESSION_IO_EVT_TX;
}
if (ctx->s->flags & SESSION_F_CUSTOM_TX)
@@ -883,7 +884,12 @@
session_tx_set_dequeue_params (vm, ctx, max_burst, peek_data);
if (PREDICT_FALSE (!ctx->max_len_to_snd))
- return SESSION_TX_NO_DATA;
+ {
+ transport_connection_tx_pacer_reset_bucket (ctx->tc,
+ vm->clib_time.
+ last_cpu_time);
+ return SESSION_TX_NO_DATA;
+ }
n_bufs_needed = ctx->n_segs_per_evt * ctx->n_bufs_per_seg;
vec_validate_aligned (wrk->tx_buffers, n_bufs_needed - 1,
diff --git a/src/vnet/session/transport.c b/src/vnet/session/transport.c
index 49a4af7..8f7e30c 100644
--- a/src/vnet/session/transport.c
+++ b/src/vnet/session/transport.c
@@ -47,10 +47,6 @@
*/
static double transport_pacer_period;
-#define TRANSPORT_PACER_MIN_MSS 1460
-#define TRANSPORT_PACER_MIN_BURST TRANSPORT_PACER_MIN_MSS
-#define TRANSPORT_PACER_MAX_BURST (43 * TRANSPORT_PACER_MIN_MSS)
-
u8 *
format_transport_proto (u8 * s, va_list * args)
{
@@ -583,6 +579,13 @@
u64 n_periods = norm_time_now - pacer->last_update;
u64 inc;
+ if (PREDICT_FALSE (n_periods > 5e5))
+ {
+ pacer->last_update = norm_time_now;
+ pacer->bucket = TRANSPORT_PACER_MIN_BURST;
+ return TRANSPORT_PACER_MIN_BURST;
+ }
+
if (n_periods > 0
&& (inc = (f32) n_periods * pacer->tokens_per_period) > 10)
{
@@ -674,7 +677,7 @@
u32 snd_space, max_paced_burst;
snd_space = tp_vfts[tc->proto].send_space (tc);
- if (transport_connection_is_tx_paced (tc))
+ if (snd_space && transport_connection_is_tx_paced (tc))
{
time_now >>= SPACER_CPU_TICKS_PER_PERIOD_SHIFT;
max_paced_burst = spacer_max_burst (&tc->pacer, time_now);
diff --git a/src/vnet/session/transport.h b/src/vnet/session/transport.h
index 5b45be0..914991d 100644
--- a/src/vnet/session/transport.h
+++ b/src/vnet/session/transport.h
@@ -19,6 +19,10 @@
#include <vnet/vnet.h>
#include <vnet/session/transport_types.h>
+#define TRANSPORT_PACER_MIN_MSS 1460
+#define TRANSPORT_PACER_MIN_BURST TRANSPORT_PACER_MIN_MSS
+#define TRANSPORT_PACER_MAX_BURST (43 * TRANSPORT_PACER_MIN_MSS)
+
typedef struct _transport_options_t
{
transport_tx_fn_type_t tx_type;
diff --git a/src/vnet/tcp/tcp.h b/src/vnet/tcp/tcp.h
index a31c46c..5e683f7 100644
--- a/src/vnet/tcp/tcp.h
+++ b/src/vnet/tcp/tcp.h
@@ -372,6 +372,7 @@
u32 prr_start; /**< snd_una when prr starts */
u32 rxt_delivered; /**< Rxt bytes delivered during current cc event */
u32 rxt_head; /**< snd_una last time we re rxted the head */
+ u32 prev_dsegs_out; /**< Number of dsegs after last ack */
u32 tsecr_last_ack; /**< Timestamp echoed to us in last healthy ACK */
u32 snd_congestion; /**< snd_una_max when congestion is detected */
u32 tx_fifo_size; /**< Tx fifo size. Used to constrain cwnd */
diff --git a/src/vnet/tcp/tcp_input.c b/src/vnet/tcp/tcp_input.c
index f177f5f..ea64e4a 100755
--- a/src/vnet/tcp/tcp_input.c
+++ b/src/vnet/tcp/tcp_input.c
@@ -574,6 +574,15 @@
tcp_update_rto (tc);
}
+always_inline u8
+tcp_recovery_no_snd_space (tcp_connection_t * tc)
+{
+ return (tcp_in_fastrecovery (tc)
+ && tcp_fastrecovery_prr_snd_space (tc) < tc->snd_mss)
+ || (tcp_in_recovery (tc)
+ && tcp_available_output_snd_space (tc) < tc->snd_mss);
+}
+
/**
* Dequeue bytes for connections that have received acks in last burst
*/
@@ -594,26 +603,35 @@
tc = tcp_connection_get (pending_deq_acked[i], thread_index);
tc->flags &= ~TCP_CONN_DEQ_PENDING;
- if (PREDICT_FALSE (!tc->burst_acked))
- continue;
-
- /* Dequeue the newly ACKed bytes */
- session_tx_fifo_dequeue_drop (&tc->connection, tc->burst_acked);
- tc->burst_acked = 0;
- tcp_validate_txf_size (tc, tc->snd_una_max - tc->snd_una);
-
- if (PREDICT_FALSE (tc->flags & TCP_CONN_PSH_PENDING))
+ if (tc->burst_acked)
{
- if (seq_leq (tc->psh_seq, tc->snd_una))
- tc->flags &= ~TCP_CONN_PSH_PENDING;
+ /* Dequeue the newly ACKed bytes */
+ session_tx_fifo_dequeue_drop (&tc->connection, tc->burst_acked);
+ tc->burst_acked = 0;
+ tcp_validate_txf_size (tc, tc->snd_una_max - tc->snd_una);
+
+ if (PREDICT_FALSE (tc->flags & TCP_CONN_PSH_PENDING))
+ {
+ if (seq_leq (tc->psh_seq, tc->snd_una))
+ tc->flags &= ~TCP_CONN_PSH_PENDING;
+ }
+
+ /* If everything has been acked, stop retransmit timer
+ * otherwise update. */
+ tcp_retransmit_timer_update (tc);
+
+ /* Update pacer based on our new cwnd estimate */
+ tcp_connection_tx_pacer_update (tc);
}
- /* If everything has been acked, stop retransmit timer
- * otherwise update. */
- tcp_retransmit_timer_update (tc);
-
- /* Update pacer based on our new cwnd estimate */
- tcp_connection_tx_pacer_update (tc);
+ /* Reset the pacer if we've been idle, i.e., no data sent or if
+ * we're in recovery and snd space constrained */
+ if (tc->data_segs_out == tc->prev_dsegs_out
+ || tcp_recovery_no_snd_space (tc))
+ transport_connection_tx_pacer_reset_bucket (&tc->connection,
+ wrk->vm->clib_time.
+ last_cpu_time);
+ tc->prev_dsegs_out = tc->data_segs_out;
}
_vec_len (wrk->pending_deq_acked) = 0;
}
@@ -1335,6 +1353,8 @@
tc->rtt_ts = 0;
tc->flags &= ~TCP_CONN_RXT_PENDING;
+ tcp_connection_tx_pacer_reset (tc, tc->cwnd, 0 /* start bucket */ );
+
/* Previous recovery left us congested. Continue sending as part
* of the current recovery event with an updated snd_congestion */
if (tc->sack_sb.sacked_bytes)
@@ -1354,8 +1374,6 @@
if (!tcp_in_recovery (tc) && !is_spurious)
tcp_cc_recovered (tc);
- tcp_connection_tx_pacer_reset (tc, tc->cwnd, 0 /* start bucket */ );
-
tcp_fastrecovery_off (tc);
tcp_fastrecovery_first_off (tc);
tcp_recovery_off (tc);
@@ -1589,11 +1607,10 @@
if (tc->flags & TCP_CONN_RATE_SAMPLE)
tcp_bt_sample_delivery_rate (tc, &rs);
+ tcp_program_dequeue (wrk, tc);
+
if (tc->bytes_acked)
- {
- tcp_program_dequeue (wrk, tc);
- tcp_update_rtt (tc, &rs, vnet_buffer (b)->tcp.ack_number);
- }
+ tcp_update_rtt (tc, &rs, vnet_buffer (b)->tcp.ack_number);
TCP_EVT (TCP_EVT_ACK_RCVD, tc);
diff --git a/src/vnet/tcp/tcp_output.c b/src/vnet/tcp/tcp_output.c
index 79866af..047247e 100644
--- a/src/vnet/tcp/tcp_output.c
+++ b/src/vnet/tcp/tcp_output.c
@@ -409,7 +409,10 @@
tc->flags |= TCP_CONN_TRACK_BURST;
if (tc->snd_una == tc->snd_nxt)
- tcp_cc_event (tc, TCP_CC_EVT_START_TX);
+ {
+ tcp_cc_event (tc, TCP_CC_EVT_START_TX);
+ tcp_connection_tx_pacer_reset (tc, tc->cwnd, TRANSPORT_PACER_MIN_MSS);
+ }
}
#endif /* CLIB_MARCH_VARIANT */
@@ -1435,19 +1438,7 @@
max_deq_bytes = clib_min (tc->snd_mss, max_deq_bytes);
max_deq_bytes = clib_min (available_bytes, max_deq_bytes);
- /* Start is beyond snd_congestion */
start = tc->snd_una + offset;
- if (seq_geq (start, tc->snd_congestion))
- return 0;
-
- /* Don't overshoot snd_congestion */
- if (seq_gt (start + max_deq_bytes, tc->snd_congestion))
- {
- max_deq_bytes = tc->snd_congestion - start;
- if (max_deq_bytes == 0)
- return 0;
- }
-
n_bytes = tcp_prepare_segment (wrk, tc, offset, max_deq_bytes, b);
if (!n_bytes)
return 0;
@@ -1903,17 +1894,28 @@
tcp_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
u32 burst_size)
{
+ u8 snd_limited = 0, can_rescue = 0, reset_pacer = 0;
u32 n_written = 0, offset, max_bytes, n_segs = 0;
+ u32 bi, max_deq, burst_bytes, sent_bytes;
sack_scoreboard_hole_t *hole;
vlib_main_t *vm = wrk->vm;
vlib_buffer_t *b = 0;
sack_scoreboard_t *sb;
- u32 bi, max_deq;
int snd_space;
- u8 snd_limited = 0, can_rescue = 0;
+ u64 time_now;
ASSERT (tcp_in_cong_recovery (tc));
+ time_now = wrk->vm->clib_time.last_cpu_time;
+ burst_bytes = transport_connection_tx_pacer_burst (&tc->connection,
+ time_now);
+ burst_size = clib_min (burst_size, burst_bytes / tc->snd_mss);
+ if (!burst_size)
+ {
+ tcp_program_retransmit (tc);
+ return 0;
+ }
+
if (tcp_in_recovery (tc))
snd_space = tcp_available_cc_snd_space (tc);
else
@@ -1921,13 +1923,12 @@
if (snd_space < tc->snd_mss)
{
- /* We're cc constrained so don't accumulate tokens */
- transport_connection_tx_pacer_reset_bucket (&tc->connection,
- vm->
- clib_time.last_cpu_time);
- return 0;
+ reset_pacer = burst_bytes > tc->snd_mss;
+ goto done;
}
+ reset_pacer = snd_space < burst_bytes;
+
sb = &tc->sack_sb;
/* Check if snd_una is a lost retransmit */
@@ -1967,9 +1968,12 @@
/* We are out of lost holes to retransmit so send some new data. */
if (max_deq > tc->snd_mss)
{
- u32 n_segs_new, av_window;
- av_window = tc->snd_wnd - (tc->snd_nxt - tc->snd_una);
- snd_space = clib_min (snd_space, av_window);
+ u32 n_segs_new;
+ int av_wnd;
+
+ av_wnd = (int) tc->snd_wnd - (tc->snd_nxt - tc->snd_una);
+ av_wnd = clib_max (av_wnd, 0);
+ snd_space = clib_min (snd_space, av_wnd);
snd_space = clib_min (max_deq, snd_space);
burst_size = clib_min (burst_size - n_segs,
snd_space / tc->snd_mss);
@@ -2034,6 +2038,19 @@
done:
+ if (reset_pacer)
+ {
+ transport_connection_tx_pacer_reset_bucket (&tc->connection,
+ vm->clib_time.
+ last_cpu_time);
+ }
+ else
+ {
+ sent_bytes = clib_min (n_segs * tc->snd_mss, burst_bytes);
+ transport_connection_tx_pacer_update_bytes (&tc->connection,
+ sent_bytes);
+ }
+
return n_segs;
}
@@ -2045,14 +2062,28 @@
u32 burst_size)
{
u32 n_written = 0, offset = 0, bi, max_deq, n_segs_now;
+ u32 burst_bytes, sent_bytes;
vlib_main_t *vm = wrk->vm;
int snd_space, n_segs = 0;
+ u8 cc_limited = 0;
vlib_buffer_t *b;
+ u64 time_now;
ASSERT (tcp_in_fastrecovery (tc));
TCP_EVT (TCP_EVT_CC_EVT, tc, 0);
+ time_now = wrk->vm->clib_time.last_cpu_time;
+ burst_bytes = transport_connection_tx_pacer_burst (&tc->connection,
+ time_now);
+ burst_size = clib_min (burst_size, burst_bytes / tc->snd_mss);
+ if (!burst_size)
+ {
+ tcp_program_retransmit (tc);
+ return 0;
+ }
+
snd_space = tcp_available_cc_snd_space (tc);
+ cc_limited = snd_space < burst_bytes;
if (!tcp_fastrecovery_first (tc))
goto send_unsent;
@@ -2098,19 +2129,12 @@
done:
tcp_fastrecovery_first_off (tc);
- return n_segs;
-}
-/**
- * Do fast retransmit
- */
-static int
-tcp_retransmit (tcp_worker_ctx_t * wrk, tcp_connection_t * tc, u32 burst_size)
-{
- if (tcp_opts_sack_permitted (&tc->rcv_opts))
- return tcp_retransmit_sack (wrk, tc, burst_size);
- else
- return tcp_retransmit_no_sack (wrk, tc, burst_size);
+ sent_bytes = clib_min (n_segs * tc->snd_mss, burst_bytes);
+ sent_bytes = cc_limited ? burst_bytes : sent_bytes;
+ transport_connection_tx_pacer_update_bytes (&tc->connection, sent_bytes);
+
+ return n_segs;
}
static int
@@ -2164,23 +2188,16 @@
static int
tcp_do_retransmit (tcp_connection_t * tc, u32 max_burst_size)
{
- u32 n_segs = 0, burst_size, sent_bytes, burst_bytes;
tcp_worker_ctx_t *wrk;
+ u32 n_segs;
wrk = tcp_get_worker (tc->c_thread_index);
- burst_bytes = transport_connection_tx_pacer_burst (&tc->connection,
- wrk->vm->
- clib_time.last_cpu_time);
- burst_size = clib_min (max_burst_size, burst_bytes / tc->snd_mss);
- if (!burst_size)
- {
- tcp_program_retransmit (tc);
- return 0;
- }
- n_segs = tcp_retransmit (wrk, tc, burst_size);
- sent_bytes = clib_min (n_segs * tc->snd_mss, burst_bytes);
- transport_connection_tx_pacer_update_bytes (&tc->connection, sent_bytes);
+ if (tcp_opts_sack_permitted (&tc->rcv_opts))
+ n_segs = tcp_retransmit_sack (wrk, tc, max_burst_size);
+ else
+ n_segs = tcp_retransmit_no_sack (wrk, tc, max_burst_size);
+
return n_segs;
}