xprtrdma: Allocate MRs on demand

Frequent MR list exhaustion can impact I/O throughput, so enough MRs
are always created during transport set-up to prevent running out.
This means more MRs are created than most workloads need.

Commit 94f58c58c0b4 ("xprtrdma: Allow Read list and Reply chunk
simultaneously") introduced support for sending two chunk lists per
RPC, which consumes more MRs per RPC.

Instead of trying to provision more MRs, introduce a mechanism for
allocating MRs on demand. A few MRs are allocated during transport
set-up to kick things off.

This significantly reduces the average number of MRs per transport
while allowing the MR count to grow for workloads or devices that
need more MRs.

FRWR with mlx4 allocated almost 400 MRs per transport before this
patch. Now it starts with 32.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 7 insertions, 57 deletions

diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index f3a06fa..e77776b 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -91,12 +91,13 @@ out_not_supported:
 }
 
 static int
-__frwr_init(struct rpcrdma_mw *r, struct ib_pd *pd, unsigned int depth)
+frwr_op_init_mr(struct rpcrdma_ia *ia, struct rpcrdma_mw *r)
 {
+	unsigned int depth = ia->ri_max_frmr_depth;
 	struct rpcrdma_frmr *f = &r->frmr;
 	int rc;
 
-	f->fr_mr = ib_alloc_mr(pd, IB_MR_TYPE_MEM_REG, depth);
+	f->fr_mr = ib_alloc_mr(ia->ri_pd, IB_MR_TYPE_MEM_REG, depth);
 	if (IS_ERR(f->fr_mr))
 		goto out_mr_err;
 
@@ -123,7 +124,7 @@ out_list_err:
 }
 
 static void
-__frwr_release(struct rpcrdma_mw *r)
+frwr_op_release_mr(struct rpcrdma_mw *r)
 {
 	int rc;
 
@@ -132,6 +133,7 @@ __frwr_release(struct rpcrdma_mw *r)
 		pr_err("rpcrdma: final ib_dereg_mr for %p returned %i\n",
 		       r, rc);
 	kfree(r->mw_sg);
+	kfree(r);
 }
 
 static int
@@ -319,45 +321,6 @@ frwr_wc_localinv_wake(struct ib_cq *cq, struct ib_wc *wc)
 	complete_all(&frmr->fr_linv_done);
 }
 
-static int
-frwr_op_init(struct rpcrdma_xprt *r_xprt)
-{
-	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
-	unsigned int depth = r_xprt->rx_ia.ri_max_frmr_depth;
-	struct ib_pd *pd = r_xprt->rx_ia.ri_pd;
-	int i;
-
-	spin_lock_init(&buf->rb_mwlock);
-	INIT_LIST_HEAD(&buf->rb_mws);
-	INIT_LIST_HEAD(&buf->rb_all);
-
-	i = max_t(int, RPCRDMA_MAX_DATA_SEGS / depth, 1);
-	i += 2;				/* head + tail */
-	i *= buf->rb_max_requests;	/* one set for each RPC slot */
-	dprintk("RPC:       %s: initalizing %d FRMRs\n", __func__, i);
-
-	while (i--) {
-		struct rpcrdma_mw *r;
-		int rc;
-
-		r = kzalloc(sizeof(*r), GFP_KERNEL);
-		if (!r)
-			return -ENOMEM;
-
-		rc = __frwr_init(r, pd, depth);
-		if (rc) {
-			kfree(r);
-			return rc;
-		}
-
-		r->mw_xprt = r_xprt;
-		list_add(&r->mw_list, &buf->rb_mws);
-		list_add(&r->mw_all, &buf->rb_all);
-	}
-
-	return 0;
-}
-
 /* Post a REG_MR Work Request to register a memory region
  * for remote access via RDMA READ or RDMA WRITE.
  */
@@ -618,19 +581,6 @@ frwr_op_unmap_safe(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 	}
 }
 
-static void
-frwr_op_destroy(struct rpcrdma_buffer *buf)
-{
-	struct rpcrdma_mw *r;
-
-	while (!list_empty(&buf->rb_all)) {
-		r = list_entry(buf->rb_all.next, struct rpcrdma_mw, mw_all);
-		list_del(&r->mw_all);
-		__frwr_release(r);
-		kfree(r);
-	}
-}
-
 const struct rpcrdma_memreg_ops rpcrdma_frwr_memreg_ops = {
 	.ro_map				= frwr_op_map,
 	.ro_unmap_sync			= frwr_op_unmap_sync,
@@ -638,7 +588,7 @@ const struct rpcrdma_memreg_ops rpcrdma_frwr_memreg_ops = {
 	.ro_recover_mr			= frwr_op_recover_mr,
 	.ro_open			= frwr_op_open,
 	.ro_maxpages			= frwr_op_maxpages,
-	.ro_init			= frwr_op_init,
-	.ro_destroy			= frwr_op_destroy,
+	.ro_init_mr			= frwr_op_init_mr,
+	.ro_release_mr			= frwr_op_release_mr,
 	.ro_displayname			= "frwr",
 };