diff options
| author | David Howells <dhowells@redhat.com> | 2022-10-03 18:49:11 +0100 |
|---|---|---|
| committer | David Howells <dhowells@redhat.com> | 2022-11-08 16:42:28 +0000 |
| commit | 1fc4fa2ac93dcf3542f2dc6f7ff88fb022da5116 (patch) | |
| tree | 8378bd7375082220a6652a08ad76dca50fd2a09a /net/rxrpc/sendmsg.c | |
| parent | 6869ddb87d475bde2da0dbd4d71270996d65cd47 (diff) | |
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 <sxw@auristor.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Diffstat (limited to 'net/rxrpc/sendmsg.c')
| -rw-r--r-- | net/rxrpc/sendmsg.c | 22 |
1 files changed, 19 insertions, 3 deletions
diff --git a/net/rxrpc/sendmsg.c b/net/rxrpc/sendmsg.c index 9b567aff3e84..e5fd8a95bf71 100644 --- a/net/rxrpc/sendmsg.c +++ b/net/rxrpc/sendmsg.c @@ -22,11 +22,27 @@ */ static bool rxrpc_check_tx_space(struct rxrpc_call *call, rxrpc_seq_t *_tx_win) { - unsigned int win_size = - min_t(unsigned int, call->tx_winsize, - call->cong_cwnd + call->cong_extra); + unsigned int win_size; rxrpc_seq_t tx_win = smp_load_acquire(&call->acks_hard_ack); + /* If we haven't transmitted anything for >1RTT, we should reset the + * congestion management state. + */ + if (ktime_before(ktime_add_us(call->tx_last_sent, + call->peer->srtt_us >> 3), + ktime_get_real())) { + if (RXRPC_TX_SMSS > 2190) + win_size = 2; + else if (RXRPC_TX_SMSS > 1095) + win_size = 3; + else + win_size = 4; + win_size += call->cong_extra; + } else { + win_size = min_t(unsigned int, call->tx_winsize, + call->cong_cwnd + call->cong_extra); + } + if (_tx_win) *_tx_win = tx_win; return call->tx_top - tx_win < win_size; |