RDS: make socket bind/release locking scheme simple and more efficient

RDS bind and release locking scheme is very inefficient. It
uses RCU for maintaining the bind hash-table which is great but
it also needs to hold spinlock for [add/remove]_bound(). So
overall usecase, the hash-table concurrent speedup doesn't pay off.
In fact blocking nature of synchronize_rcu() makes the RDS
socket shutdown too slow which hurts RDS performance since
connection shutdown and re-connect happens quite often to
maintain the RC part of the protocol.

So we make the locking scheme simpler and more efficient by
replacing spin_locks with reader/writer locks and getting rid
off rcu for bind hash-table.

In subsequent patch, we also covert the global lock with per-bucket
lock to reduce the global lock contention.

Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>

1 files changed, 0 insertions, 6 deletions

diff --git a/net/rds/af_rds.c b/net/rds/af_rds.c
index a2f28a6..dc08766 100644
--- a/net/rds/af_rds.c
+++ b/net/rds/af_rds.c
@@ -72,13 +72,7 @@ static int rds_release(struct socket *sock)
 	rds_clear_recv_queue(rs);
 	rds_cong_remove_socket(rs);
 
-	/*
-	 * the binding lookup hash uses rcu, we need to
-	 * make sure we synchronize_rcu before we free our
-	 * entry
-	 */
 	rds_remove_bound(rs);
-	synchronize_rcu();
 
 	rds_send_drop_to(rs, NULL);
 	rds_rdma_drop_keys(rs);