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>
diff --git a/net/rds/af_rds.c b/net/rds/af_rds.c
index 853c52b..937ecda 100644
--- a/net/rds/af_rds.c
+++ b/net/rds/af_rds.c
@@ -159,7 +159,8 @@
poll_wait(file, sk->sk_sleep, wait);
- poll_wait(file, &rds_poll_waitq, wait);
+ if (rs->rs_seen_congestion)
+ poll_wait(file, &rds_poll_waitq, wait);
read_lock_irqsave(&rs->rs_recv_lock, flags);
if (!rs->rs_cong_monitor) {
@@ -181,6 +182,10 @@
mask |= (POLLOUT | POLLWRNORM);
read_unlock_irqrestore(&rs->rs_recv_lock, flags);
+ /* clear state any time we wake a seen-congested socket */
+ if (mask)
+ rs->rs_seen_congestion = 0;
+
return mask;
}