> From: Håkon Bugge <haakon.bugge@xxxxxxxxxx>
> Sent: Wednesday, March 31, 2021 9:40 PM
>
> Introduce the ability for kernel ULPs to adjust the minimum RNR Retry timer.
> The INIT -> RTR transition executed by RDMA CM will be used for this
> adjustment. This avoids an additional ib_modify_qp() call.
>
> rdma_set_min_rnr_timer() must be called before the call to
> rdma_connect() on the active side and before the call to rdma_accept() on
> the passive side.
>
If you add a line or two to explain on when a specific value is set, how it improved the response time (or less retries), will be a good for future users.
> Signed-off-by: Håkon Bugge <haakon.bugge@xxxxxxxxxx>
> ---
> drivers/infiniband/core/cma.c | 23 +++++++++++++++++++++++
> drivers/infiniband/core/cma_priv.h | 2 ++
> include/rdma/rdma_cm.h | 2 ++
> 3 files changed, 27 insertions(+)
>
> diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
> index 9409651..f50dc30 100644
> --- a/drivers/infiniband/core/cma.c
> +++ b/drivers/infiniband/core/cma.c
> @@ -852,6 +852,7 @@ static void cma_id_put(struct rdma_id_private
> *id_priv)
> id_priv->id.qp_type = qp_type;
> id_priv->tos_set = false;
> id_priv->timeout_set = false;
> + id_priv->min_rnr_timer_set = false;
> id_priv->gid_type = IB_GID_TYPE_IB;
> spin_lock_init(&id_priv->lock);
> mutex_init(&id_priv->qp_mutex);
> @@ -1141,6 +1142,9 @@ int rdma_init_qp_attr(struct rdma_cm_id *id,
> struct ib_qp_attr *qp_attr,
> if ((*qp_attr_mask & IB_QP_TIMEOUT) && id_priv->timeout_set)
> qp_attr->timeout = id_priv->timeout;
>
> + if ((*qp_attr_mask & IB_QP_MIN_RNR_TIMER) && id_priv-
> >min_rnr_timer_set)
> + qp_attr->min_rnr_timer = id_priv->min_rnr_timer;
> +
> return ret;
> }
> EXPORT_SYMBOL(rdma_init_qp_attr);
> @@ -2615,6 +2619,25 @@ int rdma_set_ack_timeout(struct rdma_cm_id
> *id, u8 timeout) } EXPORT_SYMBOL(rdma_set_ack_timeout);
Please add the kdoc style comment for this new API. Refer to rdma_set_ack_timeout() as reference example.
Also mention that min_rnr_timer follows 5-bit value is encoded value of table 48 of IB spec in comment section for users.
>
> +int rdma_set_min_rnr_timer(struct rdma_cm_id *id, u8 min_rnr_timer) {
> + struct rdma_id_private *id_priv;
> +
> + /* It is a five-bit value */
> + if (min_rnr_timer & 0xe0)
> + return -EINVAL;
> +
> + if (id->qp_type != IB_QPT_RC && id->qp_type != IB_QPT_XRC_TGT)
> + return -EINVAL;
> +
> + id_priv = container_of(id, struct rdma_id_private, id);
> + id_priv->min_rnr_timer = min_rnr_timer;
> + id_priv->min_rnr_timer_set = true;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(rdma_set_min_rnr_timer);
