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/ar-internal.h | |
| 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/ar-internal.h')
| -rw-r--r-- | net/rxrpc/ar-internal.h | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index 775eb91aabb2..6bbe28ecf583 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -332,7 +332,7 @@ struct rxrpc_peer { u32 rto_j; /* Retransmission timeout in jiffies */ u8 backoff; /* Backoff timeout */ - u8 cong_cwnd; /* Congestion window size */ + u8 cong_ssthresh; /* Congestion slow-start threshold */ }; /* @@ -626,6 +626,7 @@ struct rxrpc_call { u16 tx_backoff; /* Delay to insert due to Tx failure */ u8 tx_winsize; /* Maximum size of Tx window */ #define RXRPC_TX_MAX_WINDOW 128 + ktime_t tx_last_sent; /* Last time a transmission occurred */ /* Received data tracking */ struct sk_buff_head recvmsg_queue; /* Queue of packets ready for recvmsg() */ @@ -687,10 +688,10 @@ struct rxrpc_call { * Summary of a new ACK and the changes it made to the Tx buffer packet states. */ struct rxrpc_ack_summary { + u16 nr_acks; /* Number of ACKs in packet */ + u16 nr_new_acks; /* Number of new ACKs in packet */ + u16 nr_rot_new_acks; /* Number of rotated new ACKs */ u8 ack_reason; - u8 nr_acks; /* Number of ACKs in packet */ - u8 nr_new_acks; /* Number of new ACKs in packet */ - u8 nr_rot_new_acks; /* Number of rotated new ACKs */ bool saw_nacks; /* Saw NACKs in packet */ bool new_low_nack; /* T if new low NACK found */ bool retrans_timeo; /* T if reTx due to timeout happened */ |