Messages in this thread Patch in this message |  | | From | David Howells <> | | Subject | [PATCH net-next v2 29/39] rxrpc: Fix the calculation and use of RTO | | Date | Wed, 4 Dec 2024 07:46:57 +0000 |
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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: c410bf01933e ("rxrpc: Fix the excessive initial retransmission timeout") Fixes: 37473e416234 ("rxrpc: Clean up the resend algorithm") Signed-off-by: David Howells <dhowells@redhat.com> Suggested-by: Simon Wilkinson <sxw@auristor.com> cc: Marc Dionne <marc.dionne@auristor.com> cc: "David S. Miller" <davem@davemloft.net> cc: Eric Dumazet <edumazet@google.com> cc: Jakub Kicinski <kuba@kernel.org> cc: Paolo Abeni <pabeni@redhat.com> cc: linux-afs@lists.infradead.org cc: netdev@vger.kernel.org --- net/rxrpc/call_event.c | 3 ++- net/rxrpc/rtt.c | 2 +- 2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c index f71773b18e22..4390c97e3ba6 100644 --- a/net/rxrpc/call_event.c +++ b/net/rxrpc/call_event.c @@ -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); diff --git a/net/rxrpc/rtt.c b/net/rxrpc/rtt.c index e0b7d99854b4..3f1ec8e420a6 100644 --- a/net/rxrpc/rtt.c +++ b/net/rxrpc/rtt.c @@ -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); } /*
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