For xprtrdma, the RPC Call and Reply buffers are involved in real
I/O operations.
To start with, the DMA direction of the I/O for a Call is opposite
that of a Reply.
In the current arrangement, the Reply buffer address is on a
four-byte alignment just past the call buffer. Would be friendlier
on some platforms if that was at a DMA cache alignment instead.
Because the current arrangement allocates a single memory region
which contains both buffers, the RPC Reply buffer often contains a
page boundary in it when the Call buffer is large enough (which is
frequent).
It would be a little nicer for setting up DMA operations (and
possible registration of the Reply buffer) if the two buffers were
separated, well-aligned, and contained as few page boundaries as
possible.
Now, I could just pad out the single memory region used for the pair
of buffers. But frequently that would mean a lot of unused space to
ensure the Reply buffer did not have a page boundary.
Add a separate pointer to rpc_rqst that points right to the RPC
Reply buffer. This makes no difference to xprtsock, but it will help
xprtrdma in subsequent patches.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
include/linux/sunrpc/xprt.h | 5 +++--
net/sunrpc/clnt.c | 2 +-
net/sunrpc/sched.c | 2 ++
net/sunrpc/xprtrdma/transport.c | 2 ++
4 files changed, 8 insertions(+), 3 deletions(-)
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 272c108..8e3f292 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -84,8 +84,9 @@ struct rpc_rqst {
struct list_head rq_list;
__be32 *rq_buffer; /* Call XDR encode buffer */
- size_t rq_callsize,
- rq_rcvsize;
+ size_t rq_callsize;
+ __be32 *rq_rbuffer; /* Reply XDR decode buffer */
+ size_t rq_rcvsize;
size_t rq_xmit_bytes_sent; /* total bytes sent */
size_t rq_reply_bytes_recvd; /* total reply bytes */
/* received */
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 601b3ca..4c933a8 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -1768,7 +1768,7 @@ rpc_xdr_encode(struct rpc_task *task)
req->rq_buffer,
req->rq_callsize);
xdr_buf_init(&req->rq_rcv_buf,
- (__be32 *)((char *)req->rq_buffer + req->rq_callsize),
+ req->rq_rbuffer,
req->rq_rcvsize);
p = rpc_encode_header(task);
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 6690ebc..8ed0c87 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -891,6 +891,8 @@ int rpc_malloc(struct rpc_task *task)
dprintk("RPC: %5u allocated buffer of size %zu at %p\n",
task->tk_pid, size, buf);
rqst->rq_buffer = buf->data;
+ rqst->rq_rbuffer = (__be32 *)((char *)rqst->rq_buffer +
+ rqst->rq_callsize);
return 0;
}
EXPORT_SYMBOL_GPL(rpc_malloc);
diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
index e7f222f..1f5dc19 100644
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -524,6 +524,8 @@ out:
dprintk("RPC: %s: size %zd, request 0x%p\n", __func__, size, req);
req->rl_connect_cookie = 0; /* our reserved value */
rqst->rq_buffer = req->rl_sendbuf->rg_base;
+ rqst->rq_rbuffer = (__be32 *)((char *)rqst->rq_buffer +
+ rqst->rq_rcvsize);
return 0;
out_rdmabuf:
--
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