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

Håkon Bugge
2024-09-18T08:36:12Z

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