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authorChuck Lever <chuck.lever@oracle.com>2016-05-02 14:41:14 -0400
committerAnna Schumaker <Anna.Schumaker@Netapp.com>2016-05-17 15:47:59 -0400
commitcce6deeb56aa8aad1d3154d70ea419cf25967f5c (patch)
tree0ebdba42ca4b89faab623faf6b07f9e0e135de86 /net/sunrpc
parent302d3deb20682a076e1ab551821cacfdc81c5e4f (diff)
xprtrdma: Avoid using Write list for small NFS READ requests
Avoid the latency and interrupt overhead of registering a Write chunk when handling NFS READ requests of a few hundred bytes or less. This change does not interoperate with Linux NFS/RDMA servers that do not have commit 9d11b51ce7c1 ('svcrdma: Fix send_reply() scatter/gather set-up'). Commit 9d11b51ce7c1 was introduced in v4.3, and is included in 4.2.y, 4.1.y, and 3.18.y. Oracle bug 22925946 has been filed to request that the above fix be included in the Oracle Linux UEK4 NFS/RDMA server. Red Hat bugzillas 1327280 and 1327554 have been filed to request that RHEL NFS/RDMA server backports include the above fix. Workaround: Replace the "proto=rdma,port=20049" mount options with "proto=tcp" until commit 9d11b51ce7c1 is applied to your NFS server. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Tested-by: Steve Wise <swise@opengridcomputing.com> Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Diffstat (limited to 'net/sunrpc')
-rw-r--r--net/sunrpc/xprtrdma/rpc_rdma.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 205b81b5ca9e..0105e65ad17f 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -539,15 +539,16 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
/*
* Chunks needed for results?
*
- * o Read ops return data as write chunk(s), header as inline.
* o If the expected result is under the inline threshold, all ops
* return as inline.
+ * o Large read ops return data as write chunk(s), header as
+ * inline.
* o Large non-read ops return as a single reply chunk.
*/
- if (rqst->rq_rcv_buf.flags & XDRBUF_READ)
- wtype = rpcrdma_writech;
- else if (rpcrdma_results_inline(r_xprt, rqst))
+ if (rpcrdma_results_inline(r_xprt, rqst))
wtype = rpcrdma_noch;
+ else if (rqst->rq_rcv_buf.flags & XDRBUF_READ)
+ wtype = rpcrdma_writech;
else
wtype = rpcrdma_replych;