linux-kernel - Re: [PATCH rdma-next] RDMA/rdmavt: Decouple QP and SGE lists allocations

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Date:   Tue, 11 May 2021 10:59:52 +0000
From:   Haakon Bugge <haakon.bugge@...cle.com>
To:     Leon Romanovsky <leon@...nel.org>
CC:     Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>,
        Leon Romanovsky <leonro@...dia.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        OFED mailing list <linux-rdma@...r.kernel.org>,
        Mike Marciniszyn <mike.marciniszyn@...nelisnetworks.com>
Subject: Re: [PATCH rdma-next] RDMA/rdmavt: Decouple QP and SGE lists
 allocations



> On 11 May 2021, at 12:36, Leon Romanovsky <leon@...nel.org> wrote:
> 
> From: Leon Romanovsky <leonro@...dia.com>
> 
> The rdmavt QP has fields that are both needed for the control and data
> path. Such mixed declaration caused to the very specific allocation flow
> with kzalloc_node and SGE list embedded into the struct rvt_qp.
> 
> This patch separates QP creation to two: regular memory allocation for
> the control path and specific code for the SGE list, while the access to
> the later is performed through derefenced pointer.
> 
> Such pointer and its context are expected to be in the cache, so
> performance difference is expected to be negligible, if any exists.
> 
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> ---
> Hi,
> 
> This change is needed to convert QP to core allocation scheme. In that
> scheme QP is allocated outside of the driver and size of such allocation
> is constant and can be calculated at the compile time.
> 
> Thanks
> ---
> drivers/infiniband/sw/rdmavt/qp.c | 13 ++++++++-----
> include/rdma/rdmavt_qp.h          |  2 +-
> 2 files changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/rdmavt/qp.c b/drivers/infiniband/sw/rdmavt/qp.c
> index 9d13db68283c..4522071fc220 100644
> --- a/drivers/infiniband/sw/rdmavt/qp.c
> +++ b/drivers/infiniband/sw/rdmavt/qp.c
> @@ -1077,7 +1077,7 @@ struct ib_qp *rvt_create_qp(struct ib_pd *ibpd,
> 	int err;
> 	struct rvt_swqe *swq = NULL;
> 	size_t sz;
> -	size_t sg_list_sz;
> +	size_t sg_list_sz = 0;
> 	struct ib_qp *ret = ERR_PTR(-ENOMEM);
> 	struct rvt_dev_info *rdi = ib_to_rvt(ibpd->device);
> 	void *priv = NULL;
> @@ -1125,8 +1125,6 @@ struct ib_qp *rvt_create_qp(struct ib_pd *ibpd,
> 		if (!swq)
> 			return ERR_PTR(-ENOMEM);
> 
> -		sz = sizeof(*qp);
> -		sg_list_sz = 0;
> 		if (init_attr->srq) {
> 			struct rvt_srq *srq = ibsrq_to_rvtsrq(init_attr->srq);
> 
> @@ -1136,10 +1134,13 @@ struct ib_qp *rvt_create_qp(struct ib_pd *ibpd,
> 		} else if (init_attr->cap.max_recv_sge > 1)
> 			sg_list_sz = sizeof(*qp->r_sg_list) *
> 				(init_attr->cap.max_recv_sge - 1);
> -		qp = kzalloc_node(sz + sg_list_sz, GFP_KERNEL,
> -				  rdi->dparms.node);
> +		qp = kzalloc(sizeof(*qp), GFP_KERNEL);

Why not kzalloc_node() here?


Thxs, Håkon

> 		if (!qp)
> 			goto bail_swq;
> +		qp->r_sg_list =
> +			kzalloc_node(sg_list_sz, GFP_KERNEL, rdi->dparms.node);
> +		if (!qp->r_sg_list)
> +			goto bail_qp;
> 		qp->allowed_ops = get_allowed_ops(init_attr->qp_type);
> 
> 		RCU_INIT_POINTER(qp->next, NULL);
> @@ -1327,6 +1328,7 @@ struct ib_qp *rvt_create_qp(struct ib_pd *ibpd,
> 
> bail_qp:
> 	kfree(qp->s_ack_queue);
> +	kfree(qp->r_sg_list);
> 	kfree(qp);
> 
> bail_swq:
> @@ -1761,6 +1763,7 @@ int rvt_destroy_qp(struct ib_qp *ibqp, struct ib_udata *udata)
> 	kvfree(qp->r_rq.kwq);
> 	rdi->driver_f.qp_priv_free(rdi, qp);
> 	kfree(qp->s_ack_queue);
> +	kfree(qp->r_sg_list);
> 	rdma_destroy_ah_attr(&qp->remote_ah_attr);
> 	rdma_destroy_ah_attr(&qp->alt_ah_attr);
> 	free_ud_wq_attr(qp);
> diff --git a/include/rdma/rdmavt_qp.h b/include/rdma/rdmavt_qp.h
> index 8275954f5ce6..2e58d5e6ac0e 100644
> --- a/include/rdma/rdmavt_qp.h
> +++ b/include/rdma/rdmavt_qp.h
> @@ -444,7 +444,7 @@ struct rvt_qp {
> 	/*
> 	 * This sge list MUST be last. Do not add anything below here.
> 	 */
> -	struct rvt_sge r_sg_list[] /* verified SGEs */
> +	struct rvt_sge *r_sg_list /* verified SGEs */
> 		____cacheline_aligned_in_smp;
> };
> 
> -- 
> 2.31.1
>