SUNRPC: Separate buffer pointers for RPC Call and Reply messages

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@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Chuck Lever 2016-09-15 10:55:37 -04:00 committed by Anna Schumaker
parent 3435c74aed
commit 68778945e4
4 changed files with 6 additions and 3 deletions

View File

@ -84,8 +84,9 @@ struct rpc_rqst {
struct list_head rq_list;
void *rq_buffer; /* Call XDR encode buffer */
size_t rq_callsize,
rq_rcvsize;
size_t rq_callsize;
void *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 */

View File

@ -1766,7 +1766,7 @@ rpc_xdr_encode(struct rpc_task *task)
req->rq_buffer,
req->rq_callsize);
xdr_buf_init(&req->rq_rcv_buf,
(char *)req->rq_buffer + req->rq_callsize,
req->rq_rbuffer,
req->rq_rcvsize);
p = rpc_encode_header(task);

View File

@ -891,6 +891,7 @@ 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 = (char *)rqst->rq_buffer + rqst->rq_callsize;
return 0;
}
EXPORT_SYMBOL_GPL(rpc_malloc);

View File

@ -524,6 +524,7 @@ 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 = (char *)rqst->rq_buffer + rqst->rq_rcvsize;
return 0;
out_rdmabuf: