]> git.kernelconcepts.de Git - karo-tx-linux.git/commitdiff
xprtrdma: Remove logic that constructs RDMA_MSGP type calls
authorChuck Lever <chuck.lever@oracle.com>
Mon, 3 Aug 2015 17:03:39 +0000 (13:03 -0400)
committerAnna Schumaker <Anna.Schumaker@Netapp.com>
Wed, 5 Aug 2015 20:21:27 +0000 (16:21 -0400)
RDMA_MSGP type calls insert a zero pad in the middle of the RPC
message to align the RPC request's data payload to the server's
alignment preferences. A server can then "page flip" the payload
into place to avoid a data copy in certain circumstances. However:

1. The client has to have a priori knowledge of the server's
   preferred alignment

2. Requests eligible for RDMA_MSGP are requests that are small
   enough to have been sent inline, and convey a data payload
   at the _end_ of the RPC message

Today 1. is done with a sysctl, and is a global setting that is
copied during mount. Linux does not support CCP to query the
server's preferences (RFC 5666, Section 6).

A small-ish NFSv3 WRITE might use RDMA_MSGP, but no NFSv4
compound fits bullet 2.

Thus the Linux client currently leaves RDMA_MSGP disabled. The
Linux server handles RDMA_MSGP, but does not use any special
page flipping, so it confers no benefit.

Clean up the marshaling code by removing the logic that constructs
RDMA_MSGP type calls. This also reduces the maximum send iovec size
from four to just two elements.

/proc/sys/sunrpc/rdma_inline_write_padding is a kernel API, and
thus is left in place.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Devesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
net/sunrpc/xprtrdma/rpc_rdma.c
net/sunrpc/xprtrdma/verbs.c
net/sunrpc/xprtrdma/xprt_rdma.h

index 84ea37daef36b0aa885c27e5eda950dda818949a..8e9c56429ada1cb0cf3df25c8802687420a83264 100644 (file)
@@ -297,8 +297,7 @@ out:
  * pre-registered memory buffer for this request. For small amounts
  * of data, this is efficient. The cutoff value is tunable.
  */
-static int
-rpcrdma_inline_pullup(struct rpc_rqst *rqst, int pad)
+static void rpcrdma_inline_pullup(struct rpc_rqst *rqst)
 {
        int i, npages, curlen;
        int copy_len;
@@ -310,16 +309,9 @@ rpcrdma_inline_pullup(struct rpc_rqst *rqst, int pad)
        destp = rqst->rq_svec[0].iov_base;
        curlen = rqst->rq_svec[0].iov_len;
        destp += curlen;
-       /*
-        * Do optional padding where it makes sense. Alignment of write
-        * payload can help the server, if our setting is accurate.
-        */
-       pad -= (curlen + 36/*sizeof(struct rpcrdma_msg_padded)*/);
-       if (pad < 0 || rqst->rq_slen - curlen < RPCRDMA_INLINE_PAD_THRESH)
-               pad = 0;        /* don't pad this request */
 
-       dprintk("RPC:       %s: pad %d destp 0x%p len %d hdrlen %d\n",
-               __func__, pad, destp, rqst->rq_slen, curlen);
+       dprintk("RPC:       %s: destp 0x%p len %d hdrlen %d\n",
+               __func__, destp, rqst->rq_slen, curlen);
 
        copy_len = rqst->rq_snd_buf.page_len;
 
@@ -355,7 +347,6 @@ rpcrdma_inline_pullup(struct rpc_rqst *rqst, int pad)
                page_base = 0;
        }
        /* header now contains entire send message */
-       return pad;
 }
 
 /*
@@ -380,7 +371,7 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
        struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
        struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
        char *base;
-       size_t rpclen, padlen;
+       size_t rpclen;
        ssize_t hdrlen;
        enum rpcrdma_chunktype rtype, wtype;
        struct rpcrdma_msg *headerp;
@@ -458,7 +449,6 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
        }
 
        hdrlen = RPCRDMA_HDRLEN_MIN;
-       padlen = 0;
 
        /*
         * Pull up any extra send data into the preregistered buffer.
@@ -467,43 +457,24 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
         */
        if (rtype == rpcrdma_noch) {
 
-               padlen = rpcrdma_inline_pullup(rqst,
-                                               RPCRDMA_INLINE_PAD_VALUE(rqst));
-
-               if (padlen) {
-                       headerp->rm_type = rdma_msgp;
-                       headerp->rm_body.rm_padded.rm_align =
-                               cpu_to_be32(RPCRDMA_INLINE_PAD_VALUE(rqst));
-                       headerp->rm_body.rm_padded.rm_thresh =
-                               cpu_to_be32(RPCRDMA_INLINE_PAD_THRESH);
-                       headerp->rm_body.rm_padded.rm_pempty[0] = xdr_zero;
-                       headerp->rm_body.rm_padded.rm_pempty[1] = xdr_zero;
-                       headerp->rm_body.rm_padded.rm_pempty[2] = xdr_zero;
-                       hdrlen += 2 * sizeof(u32); /* extra words in padhdr */
-                       if (wtype != rpcrdma_noch) {
-                               dprintk("RPC:       %s: invalid chunk list\n",
-                                       __func__);
-                               return -EIO;
-                       }
-               } else {
-                       headerp->rm_body.rm_nochunks.rm_empty[0] = xdr_zero;
-                       headerp->rm_body.rm_nochunks.rm_empty[1] = xdr_zero;
-                       headerp->rm_body.rm_nochunks.rm_empty[2] = xdr_zero;
-                       /* new length after pullup */
-                       rpclen = rqst->rq_svec[0].iov_len;
-                       /*
-                        * Currently we try to not actually use read inline.
-                        * Reply chunks have the desirable property that
-                        * they land, packed, directly in the target buffers
-                        * without headers, so they require no fixup. The
-                        * additional RDMA Write op sends the same amount
-                        * of data, streams on-the-wire and adds no overhead
-                        * on receive. Therefore, we request a reply chunk
-                        * for non-writes wherever feasible and efficient.
-                        */
-                       if (wtype == rpcrdma_noch)
-                               wtype = rpcrdma_replych;
-               }
+               rpcrdma_inline_pullup(rqst);
+
+               headerp->rm_body.rm_nochunks.rm_empty[0] = xdr_zero;
+               headerp->rm_body.rm_nochunks.rm_empty[1] = xdr_zero;
+               headerp->rm_body.rm_nochunks.rm_empty[2] = xdr_zero;
+               /* new length after pullup */
+               rpclen = rqst->rq_svec[0].iov_len;
+               /* Currently we try to not actually use read inline.
+                * Reply chunks have the desirable property that
+                * they land, packed, directly in the target buffers
+                * without headers, so they require no fixup. The
+                * additional RDMA Write op sends the same amount
+                * of data, streams on-the-wire and adds no overhead
+                * on receive. Therefore, we request a reply chunk
+                * for non-writes wherever feasible and efficient.
+                */
+               if (wtype == rpcrdma_noch)
+                       wtype = rpcrdma_replych;
        }
 
        if (rtype != rpcrdma_noch) {
@@ -518,9 +489,9 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
        if (hdrlen < 0)
                return hdrlen;
 
-       dprintk("RPC:       %s: %s: hdrlen %zd rpclen %zd padlen %zd"
+       dprintk("RPC:       %s: %s: hdrlen %zd rpclen %zd"
                " headerp 0x%p base 0x%p lkey 0x%x\n",
-               __func__, transfertypes[wtype], hdrlen, rpclen, padlen,
+               __func__, transfertypes[wtype], hdrlen, rpclen,
                headerp, base, rdmab_lkey(req->rl_rdmabuf));
 
        /*
@@ -539,21 +510,6 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
        req->rl_send_iov[1].lkey = rdmab_lkey(req->rl_sendbuf);
 
        req->rl_niovs = 2;
-
-       if (padlen) {
-               struct rpcrdma_ep *ep = &r_xprt->rx_ep;
-
-               req->rl_send_iov[2].addr = rdmab_addr(ep->rep_padbuf);
-               req->rl_send_iov[2].length = padlen;
-               req->rl_send_iov[2].lkey = rdmab_lkey(ep->rep_padbuf);
-
-               req->rl_send_iov[3].addr = req->rl_send_iov[1].addr + rpclen;
-               req->rl_send_iov[3].length = rqst->rq_slen - rpclen;
-               req->rl_send_iov[3].lkey = rdmab_lkey(req->rl_sendbuf);
-
-               req->rl_niovs = 4;
-       }
-
        return 0;
 }
 
index 8516d98945996b3d99a398ea302f59c668e45ab7..b4d4f6300fbcb1ecdf9b182cd88244de5278f3ad 100644 (file)
@@ -605,6 +605,12 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia,
        struct ib_cq_init_attr cq_attr = {};
        int rc, err;
 
+       if (devattr->max_sge < RPCRDMA_MAX_IOVS) {
+               dprintk("RPC:       %s: insufficient sge's available\n",
+                       __func__);
+               return -ENOMEM;
+       }
+
        /* check provider's send/recv wr limits */
        if (cdata->max_requests > devattr->max_qp_wr)
                cdata->max_requests = devattr->max_qp_wr;
@@ -617,23 +623,13 @@ 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;
        ep->rep_attr.qp_type = IB_QPT_RC;
        ep->rep_attr.port_num = ~0;
 
-       if (cdata->padding) {
-               ep->rep_padbuf = rpcrdma_alloc_regbuf(ia, cdata->padding,
-                                                     GFP_KERNEL);
-               if (IS_ERR(ep->rep_padbuf)) {
-                       rc = PTR_ERR(ep->rep_padbuf);
-                       goto out0;
-               }
-       } else
-               ep->rep_padbuf = NULL;
-
        dprintk("RPC:       %s: requested max: dtos: send %d recv %d; "
                "iovs: send %d recv %d\n",
                __func__,
@@ -716,8 +712,6 @@ out2:
                dprintk("RPC:       %s: ib_destroy_cq returned %i\n",
                        __func__, err);
 out1:
-       rpcrdma_free_regbuf(ia, ep->rep_padbuf);
-out0:
        if (ia->ri_dma_mr)
                ib_dereg_mr(ia->ri_dma_mr);
        return rc;
@@ -746,8 +740,6 @@ rpcrdma_ep_destroy(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia)
                ia->ri_id->qp = NULL;
        }
 
-       rpcrdma_free_regbuf(ia, ep->rep_padbuf);
-
        rpcrdma_clean_cq(ep->rep_attr.recv_cq);
        rc = ib_destroy_cq(ep->rep_attr.recv_cq);
        if (rc)
@@ -1279,9 +1271,11 @@ 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);
@@ -1292,22 +1286,15 @@ 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;
index 82190118b8d99dcebe743f37698cd919641823ac..8422c09043b0eef0cc2e7d88af5dfdac70acff24 100644 (file)
@@ -88,7 +88,6 @@ struct rpcrdma_ep {
        int                     rep_connected;
        struct ib_qp_init_attr  rep_attr;
        wait_queue_head_t       rep_connect_wait;
-       struct rpcrdma_regbuf   *rep_padbuf;
        struct rdma_conn_param  rep_remote_cma;
        struct sockaddr_storage rep_remote_addr;
        struct delayed_work     rep_connect_worker;
@@ -255,16 +254,18 @@ struct rpcrdma_mr_seg {           /* chunk descriptors */
        char            *mr_offset;     /* kva if no page, else offset */
 };
 
+#define RPCRDMA_MAX_IOVS       (2)
+
 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 *