From c31dc31f84961033ecb6354811e0c360b6cf5f79 Mon Sep 17 00:00:00 2001 From: Florin Coras Date: Sun, 6 Oct 2019 14:06:14 -0700 Subject: [PATCH] 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 --- src/vnet/session/session_node.c | 8 ++- src/vnet/session/transport.c | 13 +++-- src/vnet/session/transport.h | 4 ++ src/vnet/tcp/tcp.h | 1 + src/vnet/tcp/tcp_input.c | 61 ++++++++++++++-------- src/vnet/tcp/tcp_output.c | 113 +++++++++++++++++++++++----------------- 6 files changed, 124 insertions(+), 76 deletions(-) diff --git a/src/vnet/session/session_node.c b/src/vnet/session/session_node.c index 9e53718b8dd..f51b892736a 100644 --- a/src/vnet/session/session_node.c +++ b/src/vnet/session/session_node.c @@ -845,6 +845,7 @@ session_tx_fifo_read_and_snd_i (session_worker_t * wrk, { 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_fifo_read_and_snd_i (session_worker_t * wrk, 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 49a4af71111..8f7e30c8602 100644 --- a/src/vnet/session/transport.c +++ b/src/vnet/session/transport.c @@ -47,10 +47,6 @@ static clib_spinlock_t local_endpoints_lock; */ 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 @@ spacer_max_burst (spacer_t * pacer, u64 norm_time_now) 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 @@ transport_connection_snd_space (transport_connection_t * tc, u64 time_now, 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 5b45be0a0be..914991d5b31 100644 --- a/src/vnet/session/transport.h +++ b/src/vnet/session/transport.h @@ -19,6 +19,10 @@ #include #include +#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 a31c46cdacf..5e683f72dbd 100644 --- a/src/vnet/tcp/tcp.h +++ b/src/vnet/tcp/tcp.h @@ -372,6 +372,7 @@ typedef struct _tcp_connection 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 f177f5f4753..ea64e4ab754 100755 --- a/src/vnet/tcp/tcp_input.c +++ b/src/vnet/tcp/tcp_input.c @@ -574,6 +574,15 @@ tcp_estimate_initial_rtt (tcp_connection_t * tc) 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 @@ tcp_handle_postponed_dequeues (tcp_worker_ctx_t * wrk) tc = tcp_connection_get (pending_deq_acked[i], thread_index); tc->flags &= ~TCP_CONN_DEQ_PENDING; - if (PREDICT_FALSE (!tc->burst_acked)) - continue; + if (tc->burst_acked) + { + /* 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); - /* 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 (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); - /* 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); + } - /* 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 @@ tcp_cc_recover (tcp_connection_t * tc) 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 @@ tcp_cc_recover (tcp_connection_t * tc) 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 @@ process_ack: 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 79866aff03a..047247e9ebe 100644 --- a/src/vnet/tcp/tcp_output.c +++ b/src/vnet/tcp/tcp_output.c @@ -409,7 +409,10 @@ tcp_update_burst_snd_vars (tcp_connection_t * tc) 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 @@ tcp_prepare_retransmit_segment (tcp_worker_ctx_t * wrk, 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 @@ static int 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 @@ tcp_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc, 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 @@ tcp_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc, /* 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 @@ tcp_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc, 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 @@ tcp_retransmit_no_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc, 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 @@ send_unsent: 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 @@ tcp_send_acks (tcp_connection_t * tc, u32 max_burst_size) 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; } -- 2.16.6