RE: [PATCH v1 4/5] xprtrdma: Reduce required number of send SGEs

From: Parav Pandit <parav-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
To: Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>,
	"linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: RE: [PATCH v1 4/5] xprtrdma: Reduce required number of send SGEs
Date: Fri, 13 Jan 2017 18:01:36 +0000	[thread overview]
Message-ID: <VI1PR0502MB30080923A8B244BBAD059358D1780@VI1PR0502MB3008.eurprd05.prod.outlook.com> (raw)
In-Reply-To: <20170113174322.32692.66126.stgit-FYjufvaPoItvLzlybtyyYzGyq/o6K9yX@public.gmane.org>

Hi Chuck,

> -----Original Message-----
> From: linux-rdma-owner@vger.kernel.org [mailto:linux-rdma-
> owner@vger.kernel.org] On Behalf Of Chuck Lever
> Sent: Friday, January 13, 2017 11:43 AM
> To: linux-rdma@vger.kernel.org; linux-nfs@vger.kernel.org
> Subject: [PATCH v1 4/5] xprtrdma: Reduce required number of send SGEs
> diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c
> b/net/sunrpc/xprtrdma/rpc_rdma.c index 4909758..ab699f9 100644

>  /* The client can't know how large the actual reply will be. Thus it diff --git
> a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c index
> 12e8242..5dcdd0b 100644
> --- a/net/sunrpc/xprtrdma/verbs.c
> +++ b/net/sunrpc/xprtrdma/verbs.c
> @@ -488,18 +488,19 @@ static void rpcrdma_destroy_id(struct rdma_cm_id
> *id)
>   */
>  int
>  rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia,
> -				struct rpcrdma_create_data_internal *cdata)
> +		  struct rpcrdma_create_data_internal *cdata)
>  {
>  	struct rpcrdma_connect_private *pmsg = &ep->rep_cm_private;
> +	unsigned int max_qp_wr, max_sge;
>  	struct ib_cq *sendcq, *recvcq;
> -	unsigned int max_qp_wr;
>  	int rc;
> 
> -	if (ia->ri_device->attrs.max_sge < RPCRDMA_MAX_SEND_SGES) {
> -		dprintk("RPC:       %s: insufficient sge's available\n",
> -			__func__);
> +	max_sge = min(ia->ri_device->attrs.max_sge,
> RPCRDMA_MAX_SEND_SGES);
> +	if (max_sge < 3) {
> +		pr_warn("rpcrdma: HCA provides only %d send SGEs\n",
> max_sge);
>  		return -ENOMEM;
>  	}
> +	ia->ri_max_sgeno = max_sge - 3;
> 

I didn't noticed this new ri_max_sgeno variable being used in this patch set. Did I miss?
You also might want to rename it to ri_max_sge_num.
Regardless for some device with 3 SGEs, ri_max_sgeno will become zero. Is that fine?
You wanted to check for value of 5?
It would be good to have define for this minimum required 3 SGEs header file such as RPCRDMA_MIN_REQ_RECV_SGE.

>  	if (ia->ri_device->attrs.max_qp_wr <= RPCRDMA_BACKWARD_WRS) {
>  		dprintk("RPC:       %s: insufficient wqe's available\n",
> @@ -524,7 +525,7 @@ static void rpcrdma_destroy_id(struct rdma_cm_id
> *id)
>  	ep->rep_attr.cap.max_recv_wr = cdata->max_requests;
>  	ep->rep_attr.cap.max_recv_wr += RPCRDMA_BACKWARD_WRS;
>  	ep->rep_attr.cap.max_recv_wr += 1;	/* drain cqe */
> -	ep->rep_attr.cap.max_send_sge = RPCRDMA_MAX_SEND_SGES;
> +	ep->rep_attr.cap.max_send_sge = max_sge;
>  	ep->rep_attr.cap.max_recv_sge = 1;
>  	ep->rep_attr.cap.max_inline_data = 0;
>  	ep->rep_attr.sq_sig_type = IB_SIGNAL_REQ_WR; diff --git
> a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
> index f495df0c..c134d0b 100644
> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> @@ -74,6 +74,7 @@ struct rpcrdma_ia {
>  	unsigned int		ri_max_frmr_depth;
>  	unsigned int		ri_max_inline_write;
>  	unsigned int		ri_max_inline_read;
> +	unsigned int		ri_max_sgeno;
>  	bool			ri_reminv_expected;
>  	bool			ri_implicit_padding;
>  	enum ib_mr_type		ri_mrtype;
> 
> --
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