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@xxxxxxxxxx>
Tested-by: Devesh Sharma <devesh.sharma@xxxxxxxxxxxxx>
---
net/sunrpc/xprtrdma/rpc_rdma.c | 92 ++++++++++-----------------------------
net/sunrpc/xprtrdma/verbs.c | 47 +++++++-------------
net/sunrpc/xprtrdma/xprt_rdma.h | 19 ++++----
3 files changed, 51 insertions(+), 107 deletions(-)
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 84ea37d..8e9c564 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -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;
}
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 8516d98..b4d4f63 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -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;
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 8219011..8422c09 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -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 *
--
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