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xprtrdma: Reduce required number of send SGEs

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The MAX_SEND_SGES check introduced in commit 655fec6987
("xprtrdma: Use gathered Send for large inline messages") fails
for devices that have a small max_sge.

Instead of checking for a large fixed maximum number of SGEs,
check for a minimum small number. RPC-over-RDMA will switch to
using a Read chunk if an xdr_buf has more pages than can fit in
the device's max_sge limit. This is considerably better than
failing all together to mount the server.

This fix supports devices that have as few as three send SGEs
available.

Reported-by: Selvin Xavier <selvin.xavier@broadcom.com>
Reported-by: Devesh Sharma <devesh.sharma@broadcom.com>
Reported-by: Honggang Li <honli@redhat.com>
Reported-by: Ram Amrani <Ram.Amrani@cavium.com>
Fixes: 655fec6987 ("xprtrdma: Use gathered Send for large ...")
Cc: stable@vger.kernel.org # v4.9+
Tested-by: Honggang Li <honli@redhat.com>
Tested-by: Ram Amrani <Ram.Amrani@cavium.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Chuck Lever 2017-02-08 17:00:10 -05:00 committed by Anna Schumaker
parent c95a3c6b88
commit 16f906d66c
3 changed files with 32 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
net/sunrpc/xprtrdma/rpc_rdma.c
View File

@ -125,14 +125,34 @@ void rpcrdma_set_max_header_sizes(struct rpcrdma_xprt *r_xprt)
/* The client can send a request inline as long as the RPCRDMA header
* plus the RPC call fit under the transport's inline limit. If the
* combined call message size exceeds that limit, the client must use
* the read chunk list for this operation.
* a Read chunk for this operation.
*
* A Read chunk is also required if sending the RPC call inline would
* exceed this device's max_sge limit.
*/
static bool rpcrdma_args_inline(struct rpcrdma_xprt *r_xprt,
struct rpc_rqst *rqst)
{
struct rpcrdma_ia *ia = &r_xprt->rx_ia;
struct xdr_buf *xdr = &rqst->rq_snd_buf;
unsigned int count, remaining, offset;
return rqst->rq_snd_buf.len <= ia->ri_max_inline_write;
if (xdr->len > r_xprt->rx_ia.ri_max_inline_write)
return false;
if (xdr->page_len) {
remaining = xdr->page_len;
offset = xdr->page_base & ~PAGE_MASK;
count = 0;
while (remaining) {
remaining -= min_t(unsigned int,
PAGE_SIZE - offset, remaining);
offset = 0;
if (++count > r_xprt->rx_ia.ri_max_send_sges)
return false;
}
}
return true;
}
/* The client can't know how large the actual reply will be. Thus it

13
net/sunrpc/xprtrdma/verbs.c
View File

@ -488,18 +488,19 @@ rpcrdma_ia_close(struct rpcrdma_ia *ia)
*/
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 < RPCRDMA_MIN_SEND_SGES) {
pr_warn("rpcrdma: HCA provides only %d send SGEs\n", max_sge);
return -ENOMEM;
}
ia->ri_max_send_sges = max_sge - RPCRDMA_MIN_SEND_SGES;
if (ia->ri_device->attrs.max_qp_wr <= RPCRDMA_BACKWARD_WRS) {
dprintk("RPC: %s: insufficient wqe's available\n",
@ -524,7 +525,7 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia,
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;

2
net/sunrpc/xprtrdma/xprt_rdma.h
View File

@ -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_send_sges;
bool ri_reminv_expected;
bool ri_implicit_roundup;
enum ib_mr_type ri_mrtype;
@ -311,6 +312,7 @@ struct rpcrdma_mr_seg { /* chunk descriptors */
* - xdr_buf tail iovec
*/
enum {
RPCRDMA_MIN_SEND_SGES = 3,
RPCRDMA_MAX_SEND_PAGES = PAGE_SIZE + RPCRDMA_MAX_INLINE - 1,
RPCRDMA_MAX_PAGE_SGES = (RPCRDMA_MAX_SEND_PAGES >> PAGE_SHIFT) + 1,
RPCRDMA_MAX_SEND_SGES = 1 + 1 + RPCRDMA_MAX_PAGE_SGES + 1,