Re: [PATCH v1 09/12] xprtrdma: Prepare rpcrdma_ep_post() for RDMA_NOMSG calls

Devesh Sharma
2015-07-10T11:29:21Z

we need to honor the max limits of device by checking
dev_attr.max_sge? a vendor may not support 4 sges.

On Fri, Jul 10, 2015 at 2:13 AM, Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org> wrote:
> Only the RPC/RDMA header is sent when making an RDMA_NOMSG call.
> That header resides in the first element of the iovec array
> passed to rpcrdma_ep_post().
>
> Instead of special casing the iovec element with the pad, just
> sync all the elements in the send iovec. Syncing the zero pad is
> not strictly necessary, but the pad is rarely if ever used these
> days, and the extra cost in that case is small.
>
> Signed-off-by: Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> ---
> net/sunrpc/xprtrdma/rpc_rdma.c | 4 ++++
> net/sunrpc/xprtrdma/verbs.c | 27 +++++++++++----------------
> net/sunrpc/xprtrdma/xprt_rdma.h | 18 ++++++++++--------
> 3 files changed, 25 insertions(+), 24 deletions(-)
>
> diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
> index cb05233..2e721f2 100644
> --- a/net/sunrpc/xprtrdma/rpc_rdma.c
> +++ b/net/sunrpc/xprtrdma/rpc_rdma.c
> @@ -575,6 +575,10 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
> req->rl_send_iov[0].length = hdrlen;
> req->rl_send_iov[0].lkey = rdmab_lkey(req->rl_rdmabuf);
>
> + req->rl_niovs = 1;
> + if (rtype == rpcrdma_areadch)
> + return 0;
> +
> req->rl_send_iov[1].addr = rdmab_addr(req->rl_sendbuf);
> req->rl_send_iov[1].length = rpclen;
> req->rl_send_iov[1].lkey = rdmab_lkey(req->rl_sendbuf);
> diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
> index cdf5220..9199436 100644
> --- a/net/sunrpc/xprtrdma/verbs.c
> +++ b/net/sunrpc/xprtrdma/verbs.c
> @@ -651,7 +651,7 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia,
> if (rc)
> return rc;
> ep->rep_attr.cap.max_recv_wr = cdata->max_requests;
> - ep->rep_attr.cap.max_send_sge = (cdata->padding ? 4 : 2);
> + ep->rep_attr.cap.max_send_sge = RPCRDMA_MAX_IOVS;
> 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;
> @@ -1303,9 +1303,11 @@ rpcrdma_ep_post(struct rpcrdma_ia *ia,
> struct rpcrdma_ep *ep,
> struct rpcrdma_req *req)
> {
> + struct ib_device *device = ia->ri_device;
> struct ib_send_wr send_wr, *send_wr_fail;
> struct rpcrdma_rep *rep = req->rl_reply;
> - int rc;
> + struct ib_sge *iov = req->rl_send_iov;
> + int i, rc;
>
> if (rep) {
> rc = rpcrdma_ep_post_recv(ia, ep, rep);
> @@ -1316,22 +1318,15 @@ rpcrdma_ep_post(struct rpcrdma_ia *ia,
>
> send_wr.next = NULL;
> send_wr.wr_id = RPCRDMA_IGNORE_COMPLETION;
> - send_wr.sg_list = req->rl_send_iov;
> + send_wr.sg_list = iov;
> send_wr.num_sge = req->rl_niovs;
> send_wr.opcode = IB_WR_SEND;
> - if (send_wr.num_sge == 4) /* no need to sync any pad (constant) */
> - ib_dma_sync_single_for_device(ia->ri_device,
> - req->rl_send_iov[3].addr,
> - req->rl_send_iov[3].length,
> - DMA_TO_DEVICE);
> - ib_dma_sync_single_for_device(ia->ri_device,
> - req->rl_send_iov[1].addr,
> - req->rl_send_iov[1].length,
> - DMA_TO_DEVICE);
> - ib_dma_sync_single_for_device(ia->ri_device,
> - req->rl_send_iov[0].addr,
> - req->rl_send_iov[0].length,
> - DMA_TO_DEVICE);
> +
> + for (i = 0; i < send_wr.num_sge; i++)
> + ib_dma_sync_single_for_device(device, iov[i].addr,
> + iov[i].length, DMA_TO_DEVICE);
> + dprintk("RPC: %s: posting %d s/g entries\n",
> + __func__, send_wr.num_sge);
>
> if (DECR_CQCOUNT(ep) > 0)
> send_wr.send_flags = 0;
> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
> index ce4e79e..90da480 100644
> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> @@ -256,16 +256,18 @@ struct rpcrdma_mr_seg { /* chunk descriptors */
> char *mr_offset; /* kva if no page, else offset */
> };
>
> +#define RPCRDMA_MAX_IOVS (4)
> +
> struct rpcrdma_req {
> - unsigned int rl_niovs; /* 0, 2 or 4 */
> - unsigned int rl_nchunks; /* non-zero if chunks */
> - unsigned int rl_connect_cookie; /* retry detection */
> - struct rpcrdma_buffer *rl_buffer; /* home base for this structure */
> + unsigned int rl_niovs;
> + unsigned int rl_nchunks;
> + unsigned int rl_connect_cookie;
> + struct rpcrdma_buffer *rl_buffer;
> struct rpcrdma_rep *rl_reply;/* holder for reply buffer */
> - struct ib_sge rl_send_iov[4]; /* for active requests */
> - struct rpcrdma_regbuf *rl_rdmabuf;
> - struct rpcrdma_regbuf *rl_sendbuf;
> - struct rpcrdma_mr_seg rl_segments[RPCRDMA_MAX_SEGS];
> + struct ib_sge rl_send_iov[RPCRDMA_MAX_IOVS];
> + struct rpcrdma_regbuf *rl_rdmabuf;
> + struct rpcrdma_regbuf *rl_sendbuf;
> + struct rpcrdma_mr_seg rl_segments[RPCRDMA_MAX_SEGS];
> };
>
> static inline struct rpcrdma_req *
>
> --
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