RDS: only put sockets that have seen congestion on the poll_waitq

rds_poll_waitq's listeners will be awoken if we receive a congestion
notification. Bad performance may result because *all* polled sockets
contend for this single lock. However, it should not be necessary to
wake pollers when a congestion update arrives if they have never
experienced congestion, and not putting these on the waitq will
hopefully greatly reduce contention.

Signed-off-by: Andy Grover <andy.grover@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 1 deletions

diff --git a/net/rds/send.c b/net/rds/send.c
index 192a480076d0..51e2def50b12 100644
--- a/net/rds/send.c
+++ b/net/rds/send.c
@@ -894,8 +894,10 @@ int rds_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
                 queue_delayed_work(rds_wq, &conn->c_conn_w, 0);
 
         ret = rds_cong_wait(conn->c_fcong, dport, nonblock, rs);
-        if (ret)
+        if (ret) {
+                rs->rs_seen_congestion = 1;
                 goto out;
+        }
 
         while (!rds_send_queue_rm(rs, conn, rm, rs->rs_bound_port,
                                   dport, &queued)) {