RDS/IW+IB: Set recv ring low water mark to 1/2 full.

Currently the recv ring low water mark is 1/4 the depth.  Performance
measurements show that this limits iWARP throughput by flow controlling
the rds-stress senders.  Setting it to 1/2 seems to max the T3
performance.  I tried even higher levels but that didn't help and it
started to increase the rds thread cpu utilization.

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

1 files changed, 1 insertions, 1 deletions

diff --git a/net/rds/ib_ring.c b/net/rds/ib_ring.c
index 99a6ccae964c..ff97e8eda858 100644
--- a/net/rds/ib_ring.c
+++ b/net/rds/ib_ring.c
@@ -137,7 +137,7 @@ int rds_ib_ring_empty(struct rds_ib_work_ring *ring)
 
 int rds_ib_ring_low(struct rds_ib_work_ring *ring)
 {
-        return __rds_ib_ring_used(ring) <= (ring->w_nr >> 2);
+        return __rds_ib_ring_used(ring) <= (ring->w_nr >> 1);
 }
 
 /*