svcrdma: Persistently allocate and DMA-map Send buffers

While sending each RPC Reply, svc_rdma_sendto allocates and DMA-
maps a separate buffer where the RPC/RDMA transport header is
constructed. The buffer is unmapped and released in the Send
completion handler. This is significant per-RPC overhead,
especially for small RPCs.

Instead, allocate and DMA-map a buffer, and cache it in each
svc_rdma_send_ctxt. This buffer and its mapping can be re-used
for each RPC, saving the cost of memory allocation and DMA
mapping.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index a8bfc214614b..96b14a72d359 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -162,6 +162,7 @@ struct svc_rdma_send_ctxt {
         struct list_head        sc_list;
         struct ib_send_wr       sc_send_wr;
         struct ib_cqe           sc_cqe;
+        void                    *sc_xprt_buf;
         int                     sc_page_count;
         int                     sc_cur_sge_no;
         struct page             *sc_pages[RPCSVC_MAXPAGES];
@@ -199,9 +200,12 @@ extern struct svc_rdma_send_ctxt *
 extern void svc_rdma_send_ctxt_put(struct svcxprt_rdma *rdma,
                                    struct svc_rdma_send_ctxt *ctxt);
 extern int svc_rdma_send(struct svcxprt_rdma *rdma, struct ib_send_wr *wr);
-extern int svc_rdma_map_reply_hdr(struct svcxprt_rdma *rdma,
+extern void svc_rdma_sync_reply_hdr(struct svcxprt_rdma *rdma,
+                                    struct svc_rdma_send_ctxt *ctxt,
+                                    unsigned int len);
+extern int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
                                   struct svc_rdma_send_ctxt *ctxt,
-                                  __be32 *rdma_resp, unsigned int len);
+                                  struct xdr_buf *xdr, __be32 *wr_lst);
 extern int svc_rdma_sendto(struct svc_rqst *);
 
 /* svc_rdma_transport.c */