xprtrdma: Use smaller buffers for RPC-over-RDMA headers

chucklever · amschuma-ntap · commit 08cf2efd5423 · 2016-09-19T13:08:37.000-04:00
Commit 9493174 ("xprtrdma: Limit number of RDMA segments in RPC-over-RDMA headers") capped the number of chunks that may appear in RPC-over-RDMA headers. The maximum header size can be estimated and fixed to avoid allocating buffer space that is never used. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/net/sunrpc/xprtrdma/backchannel.c b/net/sunrpc/xprtrdma/backchannel.c
@@ -45,13 +45,12 @@ static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
 		return PTR_ERR(req);
 	req->rl_backchannel = true;
 
-	size = r_xprt->rx_data.inline_wsize;
-	rb = rpcrdma_alloc_regbuf(ia, size, GFP_KERNEL);
+	rb = rpcrdma_alloc_regbuf(ia, RPCRDMA_HDRBUF_SIZE, GFP_KERNEL);
 	if (IS_ERR(rb))
 		goto out_fail;
 	req->rl_rdmabuf = rb;
 
-	size += r_xprt->rx_data.inline_rsize;
+	size = r_xprt->rx_data.inline_rsize;
 	rb = rpcrdma_alloc_regbuf(ia, size, GFP_KERNEL);
 	if (IS_ERR(rb))
 		goto out_fail;
diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
@@ -484,7 +484,7 @@ static bool
 rpcrdma_get_rdmabuf(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 		    gfp_t flags)
 {
-	size_t size = r_xprt->rx_data.inline_wsize;
+	size_t size = RPCRDMA_HDRBUF_SIZE;
 	struct rpcrdma_regbuf *rb;
 
 	if (req->rl_rdmabuf)
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -160,7 +160,10 @@ rdmab_to_msg(struct rpcrdma_regbuf *rb)
  * The smallest inline threshold is 1024 bytes, ensuring that
  * at least 750 bytes are available for RPC messages.
  */
-#define RPCRDMA_MAX_HDR_SEGS	(8)
+enum {
+	RPCRDMA_MAX_HDR_SEGS = 8,
+	RPCRDMA_HDRBUF_SIZE = 256,
+};
 
 /*
  * struct rpcrdma_rep -- this structure encapsulates state required to recv

Original file line number	Diff line number	Diff line change
`@@ -484,7 +484,7 @@ static bool`
`484`	`484`	`rpcrdma_get_rdmabuf(struct rpcrdma_xprt r_xprt, struct rpcrdma_req req,`
`485`	`485`	`gfp_t flags)`
`486`	`486`	`{`
`487`		`- size_t size = r_xprt->rx_data.inline_wsize;`
	`487`	`+ size_t size = RPCRDMA_HDRBUF_SIZE;`
`488`	`488`	`struct rpcrdma_regbuf *rb;`
`489`	`489`
`490`	`490`	`if (req->rl_rdmabuf)`