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svcrdma: Clean up RPC-over-RDMA Reply header encoder 

Replace C structure-based XDR decoding with pointer arithmetic.
Pointer arithmetic is considered more portable, and is used
throughout the kernel's existing XDR encoders. The gcc optimizer
generates similar assembler code either way.

Byte-swapping before a memory store on x86 typically results in an
instruction pipeline stall. Avoid byte-swapping when encoding a new
header.

svcrdma currently doesn't alter a connection's credit grant value
after the connection has been accepted, so it is effectively a
constant. Cache the byte-swapped value in a separate field.

Christoph suggested pulling the header encoding logic into the only
function that uses it.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Chuck Lever 2017-02-07 11:58:23 -05:00 committed by J. Bruce Fields
parent cbaf58032e
commit 98fc21d3bf
4 changed files with 16 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/sunrpc/svc_rdma.h
View File

@ -141,7 +141,8 @@ struct svcxprt_rdma {
atomic_t sc_sq_avail; /* SQEs ready to be consumed */
unsigned int sc_sq_depth; /* Depth of SQ */
unsigned int sc_rq_depth; /* Depth of RQ */
u32 sc_max_requests; /* Forward credits */
__be32 sc_fc_credits; /* Forward credits */
u32 sc_max_requests; /* Max requests */
u32 sc_max_bc_requests;/* Backward credits */
int sc_max_req_size; /* Size of each RQ WR buf */
@ -214,10 +215,6 @@ extern void svc_rdma_xdr_encode_write_list(struct rpcrdma_msg *, int);
extern void svc_rdma_xdr_encode_reply_array(struct rpcrdma_write_array *, int);
extern void svc_rdma_xdr_encode_array_chunk(struct rpcrdma_write_array *, int,
__be32, __be64, u32);
extern void svc_rdma_xdr_encode_reply_header(struct svcxprt_rdma *,
struct rpcrdma_msg *,
struct rpcrdma_msg *,
enum rpcrdma_proc);
extern unsigned int svc_rdma_xdr_get_reply_hdr_len(__be32 *rdma_resp);
/* svc_rdma_recvfrom.c */

18
net/sunrpc/xprtrdma/svc_rdma_marshal.c
View File

@ -249,7 +249,7 @@ int svc_rdma_xdr_encode_error(struct svcxprt_rdma *xprt,
*va++ = rmsgp->rm_xid;
*va++ = rmsgp->rm_vers;
*va++ = cpu_to_be32(xprt->sc_max_requests);
*va++ = xprt->sc_fc_credits;
*va++ = rdma_error;
*va++ = cpu_to_be32(err);
if (err == ERR_VERS) {
@ -329,19 +329,3 @@ void svc_rdma_xdr_encode_array_chunk(struct rpcrdma_write_array *ary,
seg->rs_offset = rs_offset;
seg->rs_length = cpu_to_be32(write_len);
}
void svc_rdma_xdr_encode_reply_header(struct svcxprt_rdma *xprt,
struct rpcrdma_msg *rdma_argp,
struct rpcrdma_msg *rdma_resp,
enum rpcrdma_proc rdma_type)
{
rdma_resp->rm_xid = rdma_argp->rm_xid;
rdma_resp->rm_vers = rdma_argp->rm_vers;
rdma_resp->rm_credit = cpu_to_be32(xprt->sc_max_requests);
rdma_resp->rm_type = cpu_to_be32(rdma_type);
/* Encode <nul> chunks lists */
rdma_resp->rm_body.rm_chunks[0] = xdr_zero;
rdma_resp->rm_body.rm_chunks[1] = xdr_zero;
rdma_resp->rm_body.rm_chunks[2] = xdr_zero;
}

19
net/sunrpc/xprtrdma/svc_rdma_sendto.c
View File

@ -560,12 +560,12 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
struct rpcrdma_msg *rdma_argp;
struct rpcrdma_msg *rdma_resp;
struct rpcrdma_write_array *wr_ary, *rp_ary;
enum rpcrdma_proc reply_type;
int ret;
int inline_bytes;
struct page *res_page;
struct svc_rdma_req_map *vec;
u32 inv_rkey;
__be32 *p;
dprintk("svcrdma: sending response for rqstp=%p\n", rqstp);
@ -597,12 +597,17 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
if (!res_page)
goto err0;
rdma_resp = page_address(res_page);
if (rp_ary)
reply_type = RDMA_NOMSG;
else
reply_type = RDMA_MSG;
svc_rdma_xdr_encode_reply_header(rdma, rdma_argp,
rdma_resp, reply_type);
p = &rdma_resp->rm_xid;
*p++ = rdma_argp->rm_xid;
*p++ = rdma_argp->rm_vers;
*p++ = rdma->sc_fc_credits;
*p++ = rp_ary ? rdma_nomsg : rdma_msg;
/* Start with empty chunks */
*p++ = xdr_zero;
*p++ = xdr_zero;
*p = xdr_zero;
/* Send any write-chunk data and build resp write-list */
if (wr_ary) {

1
net/sunrpc/xprtrdma/svc_rdma_transport.c
View File

@ -1002,6 +1002,7 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
newxprt->sc_max_req_size = svcrdma_max_req_size;
newxprt->sc_max_requests = min_t(u32, dev->attrs.max_qp_wr,
svcrdma_max_requests);
newxprt->sc_fc_credits = cpu_to_be32(newxprt->sc_max_requests);
newxprt->sc_max_bc_requests = min_t(u32, dev->attrs.max_qp_wr,
svcrdma_max_bc_requests);
newxprt->sc_rq_depth = newxprt->sc_max_requests +