Re: [PATCH RFC 2/3] rdma core: Add rdma_rw_mr_payload()

[Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Tue, 2017-08-01 at 17:07 -0400, Chuck Lever wrote:
> The amount of payload per MR depends on device capabilities and
> the memory registration mode in use. The new rdma_rw API hides both,
> making it difficult for ULPs to determine how large their transport
> send queues need to be.
> 
> Expose the MR payload information via a new API.
> 
> Signed-off-by: Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>

Acked-by: Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

> ---
>  drivers/infiniband/core/rw.c |   24 ++++++++++++++++++++++++
>  include/rdma/rw.h            |    2 ++
>  2 files changed, 26 insertions(+)
> 
> diff --git a/drivers/infiniband/core/rw.c
> b/drivers/infiniband/core/rw.c
> index dbfd854..6ca607e 100644
> --- a/drivers/infiniband/core/rw.c
> +++ b/drivers/infiniband/core/rw.c
> @@ -643,6 +643,30 @@ void rdma_rw_ctx_destroy_signature(struct
> rdma_rw_ctx *ctx, struct ib_qp *qp,
>  }
>  EXPORT_SYMBOL(rdma_rw_ctx_destroy_signature);
>  
> +/**
> + * rdma_rw_mr_factor - return number of MRs required for a payload
> + * @device:	device handling the connection
> + * @port_num:	port num to which the connection is bound
> + * @maxpages:	maximum payload pages per rdma_rw_ctx
> + *
> + * Returns the number of MRs the device requires to move @maxpayload
> + * bytes. The returned value is used during transport creation to
> + * compute max_rdma_ctxts and the size of the transport's Send and
> + * Send Completion Queues.
> + */
> +unsigned int rdma_rw_mr_factor(struct ib_device *device, u8
> port_num,
> +			       unsigned int maxpages)
> +{
> +	unsigned int mr_pages;
> +
> +	if (rdma_rw_can_use_mr(device, port_num))
> +		mr_pages = rdma_rw_fr_page_list_len(device);
> +	else
> +		mr_pages = device->attrs.max_sge_rd;
> +	return DIV_ROUND_UP(maxpages, mr_pages);
> +}
> +EXPORT_SYMBOL(rdma_rw_mr_factor);
> +
>  void rdma_rw_init_qp(struct ib_device *dev, struct ib_qp_init_attr
> *attr)
>  {
>  	u32 factor;
> diff --git a/include/rdma/rw.h b/include/rdma/rw.h
> index 377d865..a3cbbc7 100644
> --- a/include/rdma/rw.h
> +++ b/include/rdma/rw.h
> @@ -81,6 +81,8 @@ struct ib_send_wr *rdma_rw_ctx_wrs(struct
> rdma_rw_ctx *ctx, struct ib_qp *qp,
>  int rdma_rw_ctx_post(struct rdma_rw_ctx *ctx, struct ib_qp *qp, u8
> port_num,
>  		struct ib_cqe *cqe, struct ib_send_wr *chain_wr);
>  
> +unsigned int rdma_rw_mr_factor(struct ib_device *device, u8
> port_num,
> +		unsigned int maxpages);
>  void rdma_rw_init_qp(struct ib_device *dev, struct ib_qp_init_attr
> *attr);
>  int rdma_rw_init_mrs(struct ib_qp *qp, struct ib_qp_init_attr
> *attr);
>  void rdma_rw_cleanup_mrs(struct ib_qp *qp);
> 
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-- 
Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
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