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>
/*
* 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;