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Commit cf1a6474 authored by David Howells's avatar David Howells
Browse files

rxrpc: Add per-peer RTT tracker 



Add a function to track the average RTT for a peer.  Sources of RTT data
will be added in subsequent patches.

The RTT data will be useful in the future for determining resend timeouts
and for handling the slow-start part of the Rx protocol.

Also add a pair of tracepoints, one to log transmissions to elicit a
response for RTT purposes and one to log responses that contribute RTT
data.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent f07373ea

include/trace/events/rxrpc.h

+61 −0
Original line number Diff line number Diff line
@@ -353,6 +353,67 @@ TRACE_EVENT(rxrpc_recvmsg, 
		      __entry->ret)

	    );



TRACE_EVENT(rxrpc_rtt_tx,

	    TP_PROTO(struct rxrpc_call *call, enum rxrpc_rtt_tx_trace why,

		     rxrpc_serial_t send_serial),



	    TP_ARGS(call, why, send_serial),



	    TP_STRUCT__entry(

		    __field(struct rxrpc_call *,	call		)

		    __field(enum rxrpc_rtt_tx_trace,	why		)

		    __field(rxrpc_serial_t,		send_serial	)

			     ),



	    TP_fast_assign(

		    __entry->call = call;

		    __entry->why = why;

		    __entry->send_serial = send_serial;

			   ),



	    TP_printk("c=%p %s sr=%08x",

		      __entry->call,

		      rxrpc_rtt_tx_traces[__entry->why],

		      __entry->send_serial)

	    );



TRACE_EVENT(rxrpc_rtt_rx,

	    TP_PROTO(struct rxrpc_call *call, enum rxrpc_rtt_rx_trace why,

		     rxrpc_serial_t send_serial, rxrpc_serial_t resp_serial,

		     s64 rtt, u8 nr, s64 avg),



	    TP_ARGS(call, why, send_serial, resp_serial, rtt, nr, avg),



	    TP_STRUCT__entry(

		    __field(struct rxrpc_call *,	call		)

		    __field(enum rxrpc_rtt_rx_trace,	why		)

		    __field(u8,				nr		)

		    __field(rxrpc_serial_t,		send_serial	)

		    __field(rxrpc_serial_t,		resp_serial	)

		    __field(s64,			rtt		)

		    __field(u64,			avg		)

			     ),



	    TP_fast_assign(

		    __entry->call = call;

		    __entry->why = why;

		    __entry->send_serial = send_serial;

		    __entry->resp_serial = resp_serial;

		    __entry->rtt = rtt;

		    __entry->nr = nr;

		    __entry->avg = avg;

			   ),



	    TP_printk("c=%p %s sr=%08x rr=%08x rtt=%lld nr=%u avg=%lld",

		      __entry->call,

		      rxrpc_rtt_rx_traces[__entry->why],

		      __entry->send_serial,

		      __entry->resp_serial,

		      __entry->rtt,

		      __entry->nr,

		      __entry->avg)

	    );



#endif /* _TRACE_RXRPC_H */



/* This part must be outside protection */

net/rxrpc/ar-internal.h

+21 −4
Original line number Diff line number Diff line
@@ -258,10 +258,11 @@ struct rxrpc_peer { 


	/* calculated RTT cache */

#define RXRPC_RTT_CACHE_SIZE 32

	suseconds_t		rtt;		/* current RTT estimate (in uS) */

	unsigned int		rtt_point;	/* next entry at which to insert */

	unsigned int		rtt_usage;	/* amount of cache actually used */

	suseconds_t		rtt_cache[RXRPC_RTT_CACHE_SIZE]; /* calculated RTT cache */

	u64			rtt;		/* Current RTT estimate (in nS) */

	u64			rtt_sum;	/* Sum of cache contents */

	u64			rtt_cache[RXRPC_RTT_CACHE_SIZE]; /* Determined RTT cache */

	u8			rtt_cursor;	/* next entry at which to insert */

	u8			rtt_usage;	/* amount of cache actually used */

};



/*
@@ -657,6 +658,20 @@ enum rxrpc_recvmsg_trace { 


extern const char rxrpc_recvmsg_traces[rxrpc_recvmsg__nr_trace][5];



enum rxrpc_rtt_tx_trace {

	rxrpc_rtt_tx_ping,

	rxrpc_rtt_tx__nr_trace

};



extern const char rxrpc_rtt_tx_traces[rxrpc_rtt_tx__nr_trace][5];



enum rxrpc_rtt_rx_trace {

	rxrpc_rtt_rx_ping_response,

	rxrpc_rtt_rx__nr_trace

};



extern const char rxrpc_rtt_rx_traces[rxrpc_rtt_rx__nr_trace][5];



extern const char *const rxrpc_pkts[];

extern const char *rxrpc_acks(u8 reason);
@@ -955,6 +970,8 @@ void rxrpc_reject_packets(struct rxrpc_local *); 
 */

void rxrpc_error_report(struct sock *);

void rxrpc_peer_error_distributor(struct work_struct *);

void rxrpc_peer_add_rtt(struct rxrpc_call *, enum rxrpc_rtt_rx_trace,

			rxrpc_serial_t, rxrpc_serial_t, ktime_t, ktime_t);



/*

 * peer_object.c

net/rxrpc/misc.c

+8 −0
Original line number Diff line number Diff line
@@ -182,3 +182,11 @@ const char rxrpc_recvmsg_traces[rxrpc_recvmsg__nr_trace][5] = { 
	[rxrpc_recvmsg_to_be_accepted]	= "TBAC",

	[rxrpc_recvmsg_return]		= "RETN",

};



const char rxrpc_rtt_tx_traces[rxrpc_rtt_tx__nr_trace][5] = {

	[rxrpc_rtt_tx_ping]		= "PING",

};



const char rxrpc_rtt_rx_traces[rxrpc_rtt_rx__nr_trace][5] = {

	[rxrpc_rtt_rx_ping_response]	= "PONG",

};

net/rxrpc/peer_event.c

+41 −0
Original line number Diff line number Diff line
@@ -305,3 +305,44 @@ void rxrpc_peer_error_distributor(struct work_struct *work) 
	rxrpc_put_peer(peer);

	_leave("");

}



/*

 * Add RTT information to cache.  This is called in softirq mode and has

 * exclusive access to the peer RTT data.

 */

void rxrpc_peer_add_rtt(struct rxrpc_call *call, enum rxrpc_rtt_rx_trace why,

			rxrpc_serial_t send_serial, rxrpc_serial_t resp_serial,

			ktime_t send_time, ktime_t resp_time)

{

	struct rxrpc_peer *peer = call->peer;

	s64 rtt;

	u64 sum = peer->rtt_sum, avg;

	u8 cursor = peer->rtt_cursor, usage = peer->rtt_usage;



	rtt = ktime_to_ns(ktime_sub(resp_time, send_time));

	if (rtt < 0)

		return;



	/* Replace the oldest datum in the RTT buffer */

	sum -= peer->rtt_cache[cursor];

	sum += rtt;

	peer->rtt_cache[cursor] = rtt;

	peer->rtt_cursor = (cursor + 1) & (RXRPC_RTT_CACHE_SIZE - 1);

	peer->rtt_sum = sum;

	if (usage < RXRPC_RTT_CACHE_SIZE) {

		usage++;

		peer->rtt_usage = usage;

	}



	/* Now recalculate the average */

	if (usage == RXRPC_RTT_CACHE_SIZE) {

		avg = sum / RXRPC_RTT_CACHE_SIZE;

	} else {

		avg = sum;

		do_div(avg, usage);

	}



	peer->rtt = avg;

	trace_rxrpc_rtt_rx(call, why, send_serial, resp_serial, rtt,

			   usage, avg);

}