udp: Improve load balancing for SO_REUSEPORT.
Currently, SO_REUSEPORT does not work well if connected sockets are in a
UDP reuseport group.
Then reuseport_has_conns() returns true and the result of
reuseport_select_sock() is discarded. Also, unconnected sockets have the
same score, hence only does the first unconnected socket in udp_hslot
always receive all packets sent to unconnected sockets.
So, the result of reuseport_select_sock() should be used for load
balancing.
The noteworthy point is that the unconnected sockets placed after
connected sockets in sock_reuseport.socks will receive more packets than
others because of the algorithm in reuseport_select_sock().
index | connected | reciprocal_scale | result
---------------------------------------------
0 | no | 20% | 40%
1 | no | 20% | 20%
2 | yes | 20% | 0%
3 | no | 20% | 40%
4 | yes | 20% | 0%
If most of the sockets are connected, this can be a problem, but it still
works better than now.
Fixes: acdcecc61285 ("udp: correct reuseport selection with connected sockets")
CC: Willem de Bruijn <willemb@google.com>
Reviewed-by: Benjamin Herrenschmidt <benh@amazon.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2 files changed