svcrdma: Maintain a Receive water mark

Post more Receives when the number of pending Receives drops below
a water mark. The batch mechanism is disabled if the underlying
device cannot support a reasonably-sized Receive Queue.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index 1e76ed6..722fc7c 100644 (file)
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -94,6 +94,8 @@ struct svcxprt_rdma {
        spinlock_t           sc_rw_ctxt_lock;
        struct list_head     sc_rw_ctxts;
 
+       u32                  sc_pending_recvs;
+       u32                  sc_recv_batch;
        struct list_head     sc_rq_dto_q;
        spinlock_t           sc_rq_dto_lock;
        struct ib_qp         *sc_qp;

diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index 1e7381f..2571188 100644 (file)
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -285,6 +285,7 @@ static bool svc_rdma_refresh_recvs(struct svcxprt_rdma *rdma,
                ctxt->rc_temp = temp;
                ctxt->rc_recv_wr.next = recv_chain;
                recv_chain = &ctxt->rc_recv_wr;
+               rdma->sc_pending_recvs++;
        }
        if (!recv_chain)
                return false;
@@ -302,6 +303,8 @@ err_free:
                bad_wr = bad_wr->next;
                svc_rdma_recv_ctxt_put(rdma, ctxt);
        }
+       /* Since we're destroying the xprt, no need to reset
+        * sc_pending_recvs. */
        return false;
 }
 
@@ -328,6 +331,8 @@ static void svc_rdma_wc_receive(struct ib_cq *cq, struct ib_wc *wc)
        struct ib_cqe *cqe = wc->wr_cqe;
        struct svc_rdma_recv_ctxt *ctxt;
 
+       rdma->sc_pending_recvs--;
+
        /* WARNING: Only wc->wr_cqe and wc->status are reliable */
        ctxt = container_of(cqe, struct svc_rdma_recv_ctxt, rc_cqe);
 
@@ -344,8 +349,9 @@ static void svc_rdma_wc_receive(struct ib_cq *cq, struct ib_wc *wc)
         * to reduce the likelihood of replayed requests once the
         * client reconnects.
         */
-       if (!svc_rdma_refresh_recvs(rdma, 1, false))
-               goto flushed;
+       if (rdma->sc_pending_recvs < rdma->sc_max_requests)
+               if (!svc_rdma_refresh_recvs(rdma, rdma->sc_recv_batch, false))
+                       goto flushed;
 
        /* All wc fields are now known to be valid */
        ctxt->rc_byte_len = wc->byte_len;

diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index 046a07d..e629eac 100644 (file)
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -407,11 +407,14 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
        newxprt->sc_max_req_size = svcrdma_max_req_size;
        newxprt->sc_max_requests = svcrdma_max_requests;
        newxprt->sc_max_bc_requests = svcrdma_max_bc_requests;
-       rq_depth = newxprt->sc_max_requests + newxprt->sc_max_bc_requests;
+       newxprt->sc_recv_batch = RPCRDMA_MAX_RECV_BATCH;
+       rq_depth = newxprt->sc_max_requests + newxprt->sc_max_bc_requests +
+                  newxprt->sc_recv_batch;
        if (rq_depth > dev->attrs.max_qp_wr) {
                pr_warn("svcrdma: reducing receive depth to %d\n",
                        dev->attrs.max_qp_wr);
                rq_depth = dev->attrs.max_qp_wr;
+               newxprt->sc_recv_batch = 1;
                newxprt->sc_max_requests = rq_depth - 2;
                newxprt->sc_max_bc_requests = 2;
        }