On Wed, 2008-10-08 at 11:48 -0400, Tom Talpey wrote:
> The RPC/RDMA protocol allows clients and servers to avoid RDMA
> operations for data which is purely the result of XDR padding.
> On the client, automatically insert the necessary padding for
> such server replies, and optionally don't marshal such chunks.
>
> Signed-off-by: Tom Talpey <talpey@xxxxxxxxxx>
> ---
>
> net/sunrpc/xprtrdma/rpc_rdma.c | 22 ++++++++++++++++++++--
> net/sunrpc/xprtrdma/transport.c | 9 +++++++++
> 2 files changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
> index 721dae7..c4b8011 100644
> --- a/net/sunrpc/xprtrdma/rpc_rdma.c
> +++ b/net/sunrpc/xprtrdma/rpc_rdma.c
> @@ -118,6 +118,11 @@ rpcrdma_convert_iovs(struct xdr_buf *xdrbuf, unsigned int pos,
> }
>
> if (xdrbuf->tail[0].iov_len) {
> + /* the rpcrdma protocol allows us to omit any trailing
> + * xdr pad bytes, saving the server an RDMA operation. */
> + extern int xprt_rdma_pad_optimize; /* 0 == old server compat */
^^^^^^^^^^^^^^^^^^^
Globals should really be declared in a header file. 'sparse' will
complain if you don't...
> + if (xdrbuf->tail[0].iov_len < 4 && xprt_rdma_pad_optimize)
> + return n;
> if (n == nsegs)
> return 0;
> seg[n].mr_page = NULL;
> @@ -594,7 +599,7 @@ rpcrdma_count_chunks(struct rpcrdma_rep *rep, unsigned int max, int wrchunk, __b
> * Scatter inline received data back into provided iov's.
> */
> static void
> -rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len)
> +rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len, int pad)
> {
> int i, npages, curlen, olen;
> char *destp;
> @@ -660,6 +665,13 @@ rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len)
> } else
> rqst->rq_rcv_buf.tail[0].iov_len = 0;
>
> + if (pad) {
> + /* implicit padding on terminal chunk */
> + unsigned char *p = rqst->rq_rcv_buf.tail[0].iov_base;
> + while (pad--)
> + p[rqst->rq_rcv_buf.tail[0].iov_len++] = 0;
> + }
> +
> if (copy_len)
> dprintk("RPC: %s: %d bytes in"
> " %d extra segments (%d lost)\n",
> @@ -794,14 +806,20 @@ repost:
> ((unsigned char *)iptr - (unsigned char *)headerp);
> status = rep->rr_len + rdmalen;
> r_xprt->rx_stats.total_rdma_reply += rdmalen;
> + /* special case - last chunk may omit padding */
> + if (rdmalen &= 3) {
> + rdmalen = 4 - rdmalen;
> + status += rdmalen;
> + }
> } else {
> /* else ordinary inline */
> + rdmalen = 0;
> iptr = (__be32 *)((unsigned char *)headerp + 28);
> rep->rr_len -= 28; /*sizeof *headerp;*/
> status = rep->rr_len;
> }
> /* Fix up the rpc results for upper layer */
> - rpcrdma_inline_fixup(rqst, (char *)iptr, rep->rr_len);
> + rpcrdma_inline_fixup(rqst, (char *)iptr, rep->rr_len, rdmalen);
> break;
>
> case __constant_htonl(RDMA_NOMSG):
> diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
> index ec6d1e7..c7d2380 100644
> --- a/net/sunrpc/xprtrdma/transport.c
> +++ b/net/sunrpc/xprtrdma/transport.c
> @@ -71,6 +71,7 @@ static unsigned int xprt_rdma_max_inline_read = RPCRDMA_DEF_INLINE;
> static unsigned int xprt_rdma_max_inline_write = RPCRDMA_DEF_INLINE;
> static unsigned int xprt_rdma_inline_write_padding;
> static unsigned int xprt_rdma_memreg_strategy = RPCRDMA_FRMR;
> + int xprt_rdma_pad_optimize = 0;
>
> #ifdef RPC_DEBUG
>
> @@ -136,6 +137,14 @@ static ctl_table xr_tunables_table[] = {
> .extra2 = &max_memreg,
> },
> {
> + .ctl_name = CTL_UNNUMBERED,
> + .procname = "rdma_pad_optimize",
> + .data = &xprt_rdma_pad_optimize,
> + .maxlen = sizeof(unsigned int),
> + .mode = 0644,
> + .proc_handler = &proc_dointvec,
> + },
> + {
> .ctl_name = 0,
> },
> };
>
> --
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