From d76470216e05867b5c59dfd06c99cbb5596cdb1a Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 3 May 2024 16:07:39 +0100 Subject: [PATCH] rxrpc: Fix congestion control algorithm BugLink: https://bugs.launchpad.net/bugs/2070349 [ Upstream commit ba4e103848d3a2a28a0445e39f4a9564187efe54 ] Make the following fixes to the congestion control algorithm: (1) Don't vary the cwnd starting value by the size of RXRPC_TX_SMSS since that's currently held constant - set to the size of a jumbo subpacket payload so that we can create jumbo packets on the fly. The current code invariably picks 3 as the starting value. Further, the starting cwnd needs to be an even number because we ack every other packet, so set it to 4. (2) Don't cut ssthresh when we see an ACK come from the peer with a receive window (rwind) less than ssthresh. ssthresh keeps track of characteristics of the connection whereas rwind may be reduced by the peer for any reason - and may be reduced to 0. Fixes: 1fc4fa2ac93d ("rxrpc: Fix congestion management") Fixes: 0851115090a3 ("rxrpc: Reduce ssthresh to peer's receive window") Signed-off-by: David Howells Suggested-by: Simon Wilkinson cc: Marc Dionne cc: linux-afs@lists.infradead.org Reviewed-by: Jeffrey Altman > Link: https://lore.kernel.org/r/20240503150749.1001323-2-dhowells@redhat.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin Signed-off-by: Manuel Diewald Signed-off-by: Stefan Bader --- net/rxrpc/ar-internal.h | 2 +- net/rxrpc/call_object.c | 7 +------ net/rxrpc/input.c | 3 --- 3 files changed, 2 insertions(+), 10 deletions(-) diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index 7818aae1be8e..4301dd20b4ea 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -692,7 +692,7 @@ struct rxrpc_call { * packets) rather than bytes. */ #define RXRPC_TX_SMSS RXRPC_JUMBO_DATALEN -#define RXRPC_MIN_CWND (RXRPC_TX_SMSS > 2190 ? 2 : RXRPC_TX_SMSS > 1095 ? 3 : 4) +#define RXRPC_MIN_CWND 4 u8 cong_cwnd; /* Congestion window size */ u8 cong_extra; /* Extra to send for congestion management */ u8 cong_ssthresh; /* Slow-start threshold */ diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c index 9fc9a6c3f685..3847b14af7f3 100644 --- a/net/rxrpc/call_object.c +++ b/net/rxrpc/call_object.c @@ -175,12 +175,7 @@ struct rxrpc_call *rxrpc_alloc_call(struct rxrpc_sock *rx, gfp_t gfp, call->rx_winsize = rxrpc_rx_window_size; call->tx_winsize = 16; - if (RXRPC_TX_SMSS > 2190) - call->cong_cwnd = 2; - else if (RXRPC_TX_SMSS > 1095) - call->cong_cwnd = 3; - else - call->cong_cwnd = 4; + call->cong_cwnd = RXRPC_MIN_CWND; call->cong_ssthresh = RXRPC_TX_MAX_WINDOW; call->rxnet = rxnet; diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c index 718ffd184ddb..f7304e06aadc 100644 --- a/net/rxrpc/input.c +++ b/net/rxrpc/input.c @@ -688,9 +688,6 @@ static void rxrpc_input_ack_trailer(struct rxrpc_call *call, struct sk_buff *skb call->tx_winsize = rwind; } - if (call->cong_ssthresh > rwind) - call->cong_ssthresh = rwind; - mtu = min(ntohl(trailer->maxMTU), ntohl(trailer->ifMTU)); peer = call->peer;