[MAINLINE 2/2] rds: ib: Add Dynamic Interrupt Moderation to CQs

["Håkon Bugge" <haakon.bugge@oracle.com>]

With the support from ib_core to use Dynamic Interrupt Moderation
(DIM) from legacy ULPs, which uses ib_create_cq(), we enable that
feature for the receive and send CQs in RDS.

A set of rds-stress runs have been done. bcopy read + write for
payload 8448 and 16640 bytes and ack/req of 256 bytes. Number of QPs
varies from 8 to 128, number of threads (i.e. rds-stress processes)
from one to 16 and a depth of four. A limit has been applied such that
the number of processes times the number of QPs never exceeds 128. All
in all, 61 rds-stress runs.

For brevity, only the rows showing a +/- 3% deviation or larger from
base is listed. The geometric mean of the ratios (IOPS_test /
IOPS_base) is calculated for all 61 runs, and that gives the best
possible "average" impact of the commits.

In the following, "base" is v6.11-rc7. "test" is the same
kernel with the following two commits:

       * rds: ib: Add Dynamic Interrupt Moderation to CQs (this commit)
       * RDMA/core: Enable legacy ULPs to use RDMA DIM

This is executed between two X8-2 with CX-5 using fw 16.35.3502. These
BM systems were instantiated with one VF, which were used for the
test:

                                 base     test
   ACK    REQ  QPS  THR  DEP     IOPS     IOPS  Percent
   256   8448    8    1    4   634463   658162      3.7
   256   8448    8    2    4   862648   997358     15.6
   256   8448    8    4    4   950458  1113991     17.2
   256   8448    8    8    4   932120  1127024     20.9
   256   8448    8   16    4   944977  1133885     20.0
  8448    256    8    2    4   858663   975563     13.6
  8448    256    8    4    4   934884  1098854     17.5
  8448    256    8    8    4   928247  1116015     20.2
  8448    256    8   16    4   938864  1123455     19.7
   256   8448   64    1    4   965985   918445     -4.9
  8448    256   64    1    4   963280   918239     -4.7
   256  16640    8    2    4   544670   582330      6.9
   256  16640    8    4    4   554873   597553      7.7
   256  16640    8    8    4   551799   597479      8.3
   256  16640    8   16    4   553041   597898      8.1
 16640    256    8    2    4   544644   578331      6.2
 16640    256    8    4    4   553944   594627      7.3
 16640    256    8    8    4   551388   594737      7.9
 16640    256    8   16    4   552986   596581      7.9
Geometric mean of ratios: 1.03

Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
---
 net/rds/ib_cm.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/rds/ib_cm.c b/net/rds/ib_cm.c
index 26b069e1999df..79603d86b6c02 100644
--- a/net/rds/ib_cm.c
+++ b/net/rds/ib_cm.c
@@ -259,6 +259,7 @@ static void rds_ib_cq_comp_handler_recv(struct ib_cq *cq, void *context)
 static void poll_scq(struct rds_ib_connection *ic, struct ib_cq *cq,
 		     struct ib_wc *wcs)
 {
+	int ncompleted = 0;
 	int nr, i;
 	struct ib_wc *wc;
 
@@ -276,7 +277,10 @@ static void poll_scq(struct rds_ib_connection *ic, struct ib_cq *cq,
 				rds_ib_mr_cqe_handler(ic, wc);
 
 		}
+		ncompleted += nr;
 	}
+	if (cq->dim)
+		rdma_dim(cq->dim, ncompleted);
 }
 
 static void rds_ib_tasklet_fn_send(unsigned long data)
@@ -304,6 +308,7 @@ static void poll_rcq(struct rds_ib_connection *ic, struct ib_cq *cq,
 		     struct ib_wc *wcs,
 		     struct rds_ib_ack_state *ack_state)
 {
+	int ncompleted = 0;
 	int nr, i;
 	struct ib_wc *wc;
 
@@ -316,7 +321,10 @@ static void poll_rcq(struct rds_ib_connection *ic, struct ib_cq *cq,
 
 			rds_ib_recv_cqe_handler(ic, wc, ack_state);
 		}
+		ncompleted += nr;
 	}
+	if (cq->dim)
+		rdma_dim(cq->dim, ncompleted);
 }
 
 static void rds_ib_tasklet_fn_recv(unsigned long data)
@@ -542,6 +550,7 @@ static int rds_ib_setup_qp(struct rds_connection *conn)
 	ic->i_scq_vector = ibdev_get_unused_vector(rds_ibdev);
 	cq_attr.cqe = ic->i_send_ring.w_nr + fr_queue_space + 1;
 	cq_attr.comp_vector = ic->i_scq_vector;
+	cq_attr.flags |= IB_CQ_MODERATE;
 	ic->i_send_cq = ib_create_cq(dev, rds_ib_cq_comp_handler_send,
 				     rds_ib_cq_event_handler, conn,
 				     &cq_attr);
@@ -556,6 +565,7 @@ static int rds_ib_setup_qp(struct rds_connection *conn)
 	ic->i_rcq_vector = ibdev_get_unused_vector(rds_ibdev);
 	cq_attr.cqe = ic->i_recv_ring.w_nr;
 	cq_attr.comp_vector = ic->i_rcq_vector;
+	cq_attr.flags |= IB_CQ_MODERATE;
 	ic->i_recv_cq = ib_create_cq(dev, rds_ib_cq_comp_handler_recv,
 				     rds_ib_cq_event_handler, conn,
 				     &cq_attr);
-- 
2.43.5