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

From: Zhu Yanjun <[email-masked]>
Date: Fri, 20 Sep 2024 15:47:19 +0800

在 2024/9/18 16:35, Håkon Bugge 写道:
> 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.

Hi, Haakon

I am interested in this patch series. I just wonder if the performance 
of rds is increased after DIM is used in legacy ULPs?
That is, is there any benefit to legacy ULPs after DIM is used?

Do you have any test results about this DIM?

Thanks,
Zhu Yanjun

> 
> 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 <[email-masked]>
> ---
>   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);