Commit 5c0ceba2 authored by David Howells's avatar David Howells Committed by Jakub Kicinski
Browse files

rxrpc: Fix the calculation and use of RTO 



Make the following changes to the calculation and use of RTO:

 (1) Fix rxrpc_resend() to use the backed-off RTO value obtained by calling
     rxrpc_get_rto_backoff() rather than extracting the value itself.
     Without this, it may retransmit packets too early.

 (2) The RTO value being similar to the RTT causes a lot of extraneous
     resends because the RTT doesn't end up taking account of clearing out
     of the receive queue on the server.  Worse, responses to PING-ACKs are
     made as fast as possible and so are less than the DATA-requested-ACK
     RTT and so skew the RTT down.

     Fix this by putting a lower bound on the RTO by adding 100ms to it and
     limiting the lower end to 200ms.

Fixes: c410bf01 ("rxrpc: Fix the excessive initial retransmission timeout")
Fixes: 37473e41 ("rxrpc: Clean up the resend algorithm")
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Suggested-by: default avatarSimon Wilkinson <sxw@auristor.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent a3d7f46d

net/rxrpc/call_event.c

+2 −1
Original line number Diff line number Diff line
@@ -103,7 +103,8 @@ void rxrpc_resend(struct rxrpc_call *call, rxrpc_serial_t ack_serial, bool ping_ 
		.now	= ktime_get_real(),

	};

	struct rxrpc_txqueue *tq = call->tx_queue;

	ktime_t lowest_xmit_ts = KTIME_MAX, rto	= ns_to_ktime(call->peer->rto_us * NSEC_PER_USEC);

	ktime_t lowest_xmit_ts = KTIME_MAX;

	ktime_t rto = rxrpc_get_rto_backoff(call->peer, false);

	bool unacked = false;



	_enter("{%d,%d}", call->tx_bottom, call->tx_top);

net/rxrpc/rtt.c

+1 −1
Original line number Diff line number Diff line
@@ -27,7 +27,7 @@ static u32 __rxrpc_set_rto(const struct rxrpc_peer *peer) 


static u32 rxrpc_bound_rto(u32 rto)

{

	return umin(rto, RXRPC_RTO_MAX);

	return clamp(200000, rto + 100000, RXRPC_RTO_MAX);

}



/*