From 57494343cb5d66962bb197878fb1cc576177db31 Mon Sep 17 00:00:00 2001 From: David Howells Date: Sat, 24 Sep 2016 18:05:27 +0100 Subject: rxrpc: Implement slow-start Implement RxRPC slow-start, which is similar to RFC 5681 for TCP. A tracepoint is added to log the state of the congestion management algorithm and the decisions it makes. Notes: (1) Since we send fixed-size DATA packets (apart from the final packet in each phase), counters and calculations are in terms of packets rather than bytes. (2) The ACK packet carries the equivalent of TCP SACK. (3) The FLIGHT_SIZE calculation in RFC 5681 doesn't seem particularly suited to SACK of a small number of packets. It seems that, almost inevitably, by the time three 'duplicate' ACKs have been seen, we have narrowed the loss down to one or two missing packets, and the FLIGHT_SIZE calculation ends up as 2. (4) In rxrpc_resend(), if there was no data that apparently needed retransmission, we transmit a PING ACK to ask the peer to tell us what its Rx window state is. Signed-off-by: David Howells --- include/trace/events/rxrpc.h | 45 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) (limited to 'include/trace') diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h index 56475497043d..ada12d00118c 100644 --- a/include/trace/events/rxrpc.h +++ b/include/trace/events/rxrpc.h @@ -570,6 +570,51 @@ TRACE_EVENT(rxrpc_retransmit, __entry->expiry) ); +TRACE_EVENT(rxrpc_congest, + TP_PROTO(struct rxrpc_call *call, struct rxrpc_ack_summary *summary, + rxrpc_serial_t ack_serial, enum rxrpc_congest_change change), + + TP_ARGS(call, summary, ack_serial, change), + + TP_STRUCT__entry( + __field(struct rxrpc_call *, call ) + __field(enum rxrpc_congest_change, change ) + __field(rxrpc_seq_t, hard_ack ) + __field(rxrpc_seq_t, top ) + __field(rxrpc_seq_t, lowest_nak ) + __field(rxrpc_serial_t, ack_serial ) + __field_struct(struct rxrpc_ack_summary, sum ) + ), + + TP_fast_assign( + __entry->call = call; + __entry->change = change; + __entry->hard_ack = call->tx_hard_ack; + __entry->top = call->tx_top; + __entry->lowest_nak = call->acks_lowest_nak; + __entry->ack_serial = ack_serial; + memcpy(&__entry->sum, summary, sizeof(__entry->sum)); + ), + + TP_printk("c=%p %08x %s %08x %s cw=%u ss=%u nr=%u,%u nw=%u,%u r=%u b=%u u=%u d=%u l=%x%s%s%s", + __entry->call, + __entry->ack_serial, + rxrpc_ack_names[__entry->sum.ack_reason], + __entry->hard_ack, + rxrpc_congest_modes[__entry->sum.mode], + __entry->sum.cwnd, + __entry->sum.ssthresh, + __entry->sum.nr_acks, __entry->sum.nr_nacks, + __entry->sum.nr_new_acks, __entry->sum.nr_new_nacks, + __entry->sum.nr_rot_new_acks, + __entry->top - __entry->hard_ack, + __entry->sum.cumulative_acks, + __entry->sum.dup_acks, + __entry->lowest_nak, __entry->sum.new_low_nack ? "!" : "", + rxrpc_congest_changes[__entry->change], + __entry->sum.retrans_timeo ? " rTxTo" : "") + ); + #endif /* _TRACE_RXRPC_H */ /* This part must be outside protection */ -- cgit v1.2.1