From 1fc4fa2ac93dcf3542f2dc6f7ff88fb022da5116 Mon Sep 17 00:00:00 2001 From: David Howells Date: Mon, 3 Oct 2022 18:49:11 +0100 Subject: rxrpc: Fix congestion management rxrpc has a problem in its congestion management in that it saves the congestion window size (cwnd) from one call to another, but if this is 0 at the time is saved, then the next call may not actually manage to ever transmit anything. To this end: (1) Don't save cwnd between calls, but rather reset back down to the initial cwnd and re-enter slow-start if data transmission is idle for more than an RTT. (2) Preserve ssthresh instead, as that is a handy estimate of pipe capacity. Knowing roughly when to stop slow start and enter congestion avoidance can reduce the tendency to overshoot and drop larger amounts of packets when probing. In future, cwind growth also needs to be constrained when the window isn't being filled due to being application limited. Reported-by: Simon Wilkinson cc: Marc Dionne cc: linux-afs@lists.infradead.org --- include/trace/events/rxrpc.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/trace') diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h index a11de55c3c14..b9886d1df825 100644 --- a/include/trace/events/rxrpc.h +++ b/include/trace/events/rxrpc.h @@ -193,6 +193,7 @@ EM(rxrpc_cong_new_low_nack, " NewLowN") \ EM(rxrpc_cong_no_change, " -") \ EM(rxrpc_cong_progress, " Progres") \ + EM(rxrpc_cong_idle_reset, " IdleRes") \ EM(rxrpc_cong_retransmit_again, " ReTxAgn") \ EM(rxrpc_cong_rtt_window_end, " RttWinE") \ E_(rxrpc_cong_saw_nack, " SawNack") -- cgit v1.2.3