[rds-devel] [PATCH ofed-1.4.1] RDS/IW+IB: Set recv ring low water mark to 1/2 full.

[Steve Wise]

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 at opengridcomputing.com>
---

 net/rds/ib_ring.c |    2 +-
 net/rds/iw_ring.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/rds/ib_ring.c b/net/rds/ib_ring.c
index d23cc59..ffd2dc8 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);
 }
 
 /*
diff --git a/net/rds/iw_ring.c b/net/rds/iw_ring.c
index d422d4b..da8e3b6 100644
--- a/net/rds/iw_ring.c
+++ b/net/rds/iw_ring.c
@@ -137,7 +137,7 @@ int rds_iw_ring_empty(struct rds_iw_work_ring *ring)
 
 int rds_iw_ring_low(struct rds_iw_work_ring *ring)
 {
-	return __rds_iw_ring_used(ring) <= (ring->w_nr >> 2);
+	return __rds_iw_ring_used(ring) <= (ring->w_nr >> 1);
 }