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svcrdma: Persistently allocate and DMA-map Send buffers

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While sending each RPC Reply, svc_rdma_sendto allocates and DMA-
maps a separate buffer where the RPC/RDMA transport header is
constructed. The buffer is unmapped and released in the Send
completion handler. This is significant per-RPC overhead,
especially for small RPCs.

Instead, allocate and DMA-map a buffer, and cache it in each
svc_rdma_send_ctxt. This buffer and its mapping can be re-used
for each RPC, saving the cost of memory allocation and DMA
mapping.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Chuck Lever 2018-05-07 15:28:25 -04:00 committed by J. Bruce Fields
parent 3abb03face
commit 99722fe4d5
4 changed files with 105 additions and 128 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/sunrpc/svc_rdma.h
View File

@ -162,6 +162,7 @@ struct svc_rdma_send_ctxt {
struct list_head sc_list;
struct ib_send_wr sc_send_wr;
struct ib_cqe sc_cqe;
void *sc_xprt_buf;
int sc_page_count;
int sc_cur_sge_no;
struct page *sc_pages[RPCSVC_MAXPAGES];
@ -199,9 +200,12 @@ extern struct svc_rdma_send_ctxt *
extern void svc_rdma_send_ctxt_put(struct svcxprt_rdma *rdma,
struct svc_rdma_send_ctxt *ctxt);
extern int svc_rdma_send(struct svcxprt_rdma *rdma, struct ib_send_wr *wr);
extern int svc_rdma_map_reply_hdr(struct svcxprt_rdma *rdma,
extern void svc_rdma_sync_reply_hdr(struct svcxprt_rdma *rdma,
struct svc_rdma_send_ctxt *ctxt,
__be32 *rdma_resp, unsigned int len);
unsigned int len);
extern int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
struct svc_rdma_send_ctxt *ctxt,
struct xdr_buf *xdr, __be32 *wr_lst);
extern int svc_rdma_sendto(struct svc_rqst *);
/* svc_rdma_transport.c */

51
net/sunrpc/xprtrdma/svc_rdma_backchannel.c
View File

@ -115,43 +115,21 @@ out_notfound:
* the adapter has a small maximum SQ depth.
*/
static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
struct rpc_rqst *rqst)
struct rpc_rqst *rqst,
struct svc_rdma_send_ctxt *ctxt)
{
struct svc_rdma_send_ctxt *ctxt;
int ret;
ctxt = svc_rdma_send_ctxt_get(rdma);
if (!ctxt) {
ret = -ENOMEM;
goto out_err;
}
/* rpcrdma_bc_send_request builds the transport header and
* the backchannel RPC message in the same buffer. Thus only
* one SGE is needed to send both.
*/
ret = svc_rdma_map_reply_hdr(rdma, ctxt, rqst->rq_buffer,
rqst->rq_snd_buf.len);
ret = svc_rdma_map_reply_msg(rdma, ctxt, &rqst->rq_snd_buf, NULL);
if (ret < 0)
goto out_err;
return -EIO;
/* Bump page refcnt so Send completion doesn't release
* the rq_buffer before all retransmits are complete.
*/
get_page(virt_to_page(rqst->rq_buffer));
ctxt->sc_send_wr.opcode = IB_WR_SEND;
ret = svc_rdma_send(rdma, &ctxt->sc_send_wr);
if (ret)
goto out_unmap;
out_err:
dprintk("svcrdma: %s returns %d\n", __func__, ret);
return ret;
out_unmap:
svc_rdma_send_ctxt_put(rdma, ctxt);
ret = -EIO;
goto out_err;
return svc_rdma_send(rdma, &ctxt->sc_send_wr);
}
/* Server-side transport endpoint wants a whole page for its send
@ -198,13 +176,15 @@ rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
{
struct rpc_xprt *xprt = rqst->rq_xprt;
struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
struct svc_rdma_send_ctxt *ctxt;
__be32 *p;
int rc;
/* Space in the send buffer for an RPC/RDMA header is reserved
* via xprt->tsh_size.
*/
p = rqst->rq_buffer;
ctxt = svc_rdma_send_ctxt_get(rdma);
if (!ctxt)
goto drop_connection;
p = ctxt->sc_xprt_buf;
*p++ = rqst->rq_xid;
*p++ = rpcrdma_version;
*p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
@ -212,14 +192,17 @@ rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
*p++ = xdr_zero;
*p++ = xdr_zero;
*p = xdr_zero;
svc_rdma_sync_reply_hdr(rdma, ctxt, RPCRDMA_HDRLEN_MIN);
#ifdef SVCRDMA_BACKCHANNEL_DEBUG
pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
#endif
rc = svc_rdma_bc_sendto(rdma, rqst);
if (rc)
rc = svc_rdma_bc_sendto(rdma, rqst, ctxt);
if (rc) {
svc_rdma_send_ctxt_put(rdma, ctxt);
goto drop_connection;
}
return rc;
drop_connection:
@ -327,7 +310,7 @@ xprt_setup_rdma_bc(struct xprt_create *args)
xprt->idle_timeout = RPCRDMA_IDLE_DISC_TO;
xprt->prot = XPRT_TRANSPORT_BC_RDMA;
xprt->tsh_size = RPCRDMA_HDRLEN_MIN / sizeof(__be32);
xprt->tsh_size = 0;
xprt->ops = &xprt_rdma_bc_procs;
memcpy(&xprt->addr, args->dstaddr, args->addrlen);

25
net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
View File

@ -602,17 +602,15 @@ static void svc_rdma_send_error(struct svcxprt_rdma *xprt,
__be32 *rdma_argp, int status)
{
struct svc_rdma_send_ctxt *ctxt;
__be32 *p, *err_msgp;
unsigned int length;
struct page *page;
__be32 *p;
int ret;
page = alloc_page(GFP_KERNEL);
if (!page)
ctxt = svc_rdma_send_ctxt_get(xprt);
if (!ctxt)
return;
err_msgp = page_address(page);
p = err_msgp;
p = ctxt->sc_xprt_buf;
*p++ = *rdma_argp;
*p++ = *(rdma_argp + 1);
*p++ = xprt->sc_fc_credits;
@ -628,19 +626,8 @@ static void svc_rdma_send_error(struct svcxprt_rdma *xprt,
*p++ = err_chunk;
trace_svcrdma_err_chunk(*rdma_argp);
}
length = (unsigned long)p - (unsigned long)err_msgp;
/* Map transport header; no RPC message payload */
ctxt = svc_rdma_send_ctxt_get(xprt);
if (!ctxt)
return;
ret = svc_rdma_map_reply_hdr(xprt, ctxt, err_msgp, length);
if (ret) {
dprintk("svcrdma: Error %d mapping send for protocol error\n",
ret);
return;
}
length = (unsigned long)p - (unsigned long)ctxt->sc_xprt_buf;
svc_rdma_sync_reply_hdr(xprt, ctxt, length);
ctxt->sc_send_wr.opcode = IB_WR_SEND;
ret = svc_rdma_send(xprt, &ctxt->sc_send_wr);

141
net/sunrpc/xprtrdma/svc_rdma_sendto.c
View File

@ -127,6 +127,8 @@ static struct svc_rdma_send_ctxt *
svc_rdma_send_ctxt_alloc(struct svcxprt_rdma *rdma)
{
struct svc_rdma_send_ctxt *ctxt;
dma_addr_t addr;
void *buffer;
size_t size;
int i;
@ -134,16 +136,33 @@ svc_rdma_send_ctxt_alloc(struct svcxprt_rdma *rdma)
size += rdma->sc_max_send_sges * sizeof(struct ib_sge);
ctxt = kmalloc(size, GFP_KERNEL);
if (!ctxt)
return NULL;
goto fail0;
buffer = kmalloc(rdma->sc_max_req_size, GFP_KERNEL);
if (!buffer)
goto fail1;
addr = ib_dma_map_single(rdma->sc_pd->device, buffer,
rdma->sc_max_req_size, DMA_TO_DEVICE);
if (ib_dma_mapping_error(rdma->sc_pd->device, addr))
goto fail2;
ctxt->sc_cqe.done = svc_rdma_wc_send;
ctxt->sc_send_wr.next = NULL;
ctxt->sc_send_wr.wr_cqe = &ctxt->sc_cqe;
ctxt->sc_send_wr.sg_list = ctxt->sc_sges;
ctxt->sc_send_wr.send_flags = IB_SEND_SIGNALED;
ctxt->sc_cqe.done = svc_rdma_wc_send;
ctxt->sc_xprt_buf = buffer;
ctxt->sc_sges[0].addr = addr;
for (i = 0; i < rdma->sc_max_send_sges; i++)
ctxt->sc_sges[i].lkey = rdma->sc_pd->local_dma_lkey;
return ctxt;
fail2:
kfree(buffer);
fail1:
kfree(ctxt);
fail0:
return NULL;
}
/**
@ -157,6 +176,11 @@ void svc_rdma_send_ctxts_destroy(struct svcxprt_rdma *rdma)
while ((ctxt = svc_rdma_next_send_ctxt(&rdma->sc_send_ctxts))) {
list_del(&ctxt->sc_list);
ib_dma_unmap_single(rdma->sc_pd->device,
ctxt->sc_sges[0].addr,
rdma->sc_max_req_size,
DMA_TO_DEVICE);
kfree(ctxt->sc_xprt_buf);
kfree(ctxt);
}
}
@ -181,6 +205,7 @@ struct svc_rdma_send_ctxt *svc_rdma_send_ctxt_get(struct svcxprt_rdma *rdma)
out:
ctxt->sc_send_wr.num_sge = 0;
ctxt->sc_cur_sge_no = 0;
ctxt->sc_page_count = 0;
return ctxt;
@ -205,7 +230,10 @@ void svc_rdma_send_ctxt_put(struct svcxprt_rdma *rdma,
struct ib_device *device = rdma->sc_cm_id->device;
unsigned int i;
for (i = 0; i < ctxt->sc_send_wr.num_sge; i++)
/* The first SGE contains the transport header, which
* remains mapped until @ctxt is destroyed.
*/
for (i = 1; i < ctxt->sc_send_wr.num_sge; i++)
ib_dma_unmap_page(device,
ctxt->sc_sges[i].addr,
ctxt->sc_sges[i].length,
@ -519,33 +547,35 @@ static int svc_rdma_dma_map_buf(struct svcxprt_rdma *rdma,
}
/**
* svc_rdma_map_reply_hdr - DMA map the transport header buffer
* svc_rdma_sync_reply_hdr - DMA sync the transport header buffer
* @rdma: controlling transport
* @ctxt: op_ctxt for the Send WR
* @rdma_resp: buffer containing transport header
* @ctxt: send_ctxt for the Send WR
* @len: length of transport header
*
* Returns:
* %0 if the header is DMA mapped,
* %-EIO if DMA mapping failed.
*/
int svc_rdma_map_reply_hdr(struct svcxprt_rdma *rdma,
void svc_rdma_sync_reply_hdr(struct svcxprt_rdma *rdma,
struct svc_rdma_send_ctxt *ctxt,
__be32 *rdma_resp,
unsigned int len)
{
ctxt->sc_pages[0] = virt_to_page(rdma_resp);
ctxt->sc_page_count++;
ctxt->sc_cur_sge_no = 0;
return svc_rdma_dma_map_page(rdma, ctxt, ctxt->sc_pages[0], 0, len);
ctxt->sc_sges[0].length = len;
ctxt->sc_send_wr.num_sge++;
ib_dma_sync_single_for_device(rdma->sc_pd->device,
ctxt->sc_sges[0].addr, len,
DMA_TO_DEVICE);
}
/* Load the xdr_buf into the ctxt's sge array, and DMA map each
/* svc_rdma_map_reply_msg - Map the buffer holding RPC message
* @rdma: controlling transport
* @ctxt: send_ctxt for the Send WR
* @xdr: prepared xdr_buf containing RPC message
* @wr_lst: pointer to Call header's Write list, or NULL
*
* Load the xdr_buf into the ctxt's sge array, and DMA map each
* element as it is added.
*
* Returns zero on success, or a negative errno on failure.
*/
static int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
struct svc_rdma_send_ctxt *ctxt,
struct xdr_buf *xdr, __be32 *wr_lst)
{
@ -624,7 +654,7 @@ static void svc_rdma_save_io_pages(struct svc_rqst *rqstp,
ctxt->sc_page_count += pages;
for (i = 0; i < pages; i++) {
ctxt->sc_pages[i + 1] = rqstp->rq_respages[i];
ctxt->sc_pages[i] = rqstp->rq_respages[i];
rqstp->rq_respages[i] = NULL;
}
rqstp->rq_next_page = rqstp->rq_respages + 1;
@ -649,27 +679,18 @@ static void svc_rdma_save_io_pages(struct svc_rqst *rqstp,
* - The Reply's transport header will never be larger than a page.
*/
static int svc_rdma_send_reply_msg(struct svcxprt_rdma *rdma,
__be32 *rdma_argp, __be32 *rdma_resp,
struct svc_rdma_send_ctxt *ctxt,
__be32 *rdma_argp,
struct svc_rqst *rqstp,
__be32 *wr_lst, __be32 *rp_ch)
{
struct svc_rdma_send_ctxt *ctxt;
int ret;
ctxt = svc_rdma_send_ctxt_get(rdma);
if (!ctxt)
return -ENOMEM;
ret = svc_rdma_map_reply_hdr(rdma, ctxt, rdma_resp,
svc_rdma_reply_hdr_len(rdma_resp));
if (ret < 0)
goto err;
if (!rp_ch) {
ret = svc_rdma_map_reply_msg(rdma, ctxt,
&rqstp->rq_res, wr_lst);
if (ret < 0)
goto err;
return ret;
}
svc_rdma_save_io_pages(rqstp, ctxt);
@ -683,15 +704,7 @@ static int svc_rdma_send_reply_msg(struct svcxprt_rdma *rdma,
}
dprintk("svcrdma: posting Send WR with %u sge(s)\n",
ctxt->sc_send_wr.num_sge);
ret = svc_rdma_send(rdma, &ctxt->sc_send_wr);
if (ret)
goto err;
return 0;
err:
svc_rdma_send_ctxt_put(rdma, ctxt);
return ret;
return svc_rdma_send(rdma, &ctxt->sc_send_wr);
}
/* Given the client-provided Write and Reply chunks, the server was not
@ -702,40 +715,29 @@ err:
* Remote Invalidation is skipped for simplicity.
*/
static int svc_rdma_send_error_msg(struct svcxprt_rdma *rdma,
__be32 *rdma_resp, struct svc_rqst *rqstp)
struct svc_rdma_send_ctxt *ctxt,
struct svc_rqst *rqstp)
{
struct svc_rdma_send_ctxt *ctxt;
__be32 *p;
int ret;
ctxt = svc_rdma_send_ctxt_get(rdma);
if (!ctxt)
return -ENOMEM;
/* Replace the original transport header with an
* RDMA_ERROR response. XID etc are preserved.
*/
trace_svcrdma_err_chunk(*rdma_resp);
p = rdma_resp + 3;
p = ctxt->sc_xprt_buf;
trace_svcrdma_err_chunk(*p);
p += 3;
*p++ = rdma_error;
*p = err_chunk;
ret = svc_rdma_map_reply_hdr(rdma, ctxt, rdma_resp, 20);
if (ret < 0)
goto err;
svc_rdma_sync_reply_hdr(rdma, ctxt, RPCRDMA_HDRLEN_ERR);
svc_rdma_save_io_pages(rqstp, ctxt);
ctxt->sc_send_wr.opcode = IB_WR_SEND;
ret = svc_rdma_send(rdma, &ctxt->sc_send_wr);
if (ret)
goto err;
return 0;
err:
if (ret) {
svc_rdma_send_ctxt_put(rdma, ctxt);
return ret;
}
return 0;
}
void svc_rdma_prep_reply_hdr(struct svc_rqst *rqstp)
@ -762,7 +764,7 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
struct svc_rdma_recv_ctxt *rctxt = rqstp->rq_xprt_ctxt;
__be32 *p, *rdma_argp, *rdma_resp, *wr_lst, *rp_ch;
struct xdr_buf *xdr = &rqstp->rq_res;
struct page *res_page;
struct svc_rdma_send_ctxt *sctxt;
int ret;
rdma_argp = rctxt->rc_recv_buf;
@ -775,10 +777,10 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
* critical section.
*/
ret = -ENOMEM;
res_page = alloc_page(GFP_KERNEL);
if (!res_page)
sctxt = svc_rdma_send_ctxt_get(rdma);
if (!sctxt)
goto err0;
rdma_resp = page_address(res_page);
rdma_resp = sctxt->sc_xprt_buf;
p = rdma_resp;
*p++ = *rdma_argp;
@ -805,10 +807,11 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
svc_rdma_xdr_encode_reply_chunk(rdma_resp, rp_ch, ret);
}
ret = svc_rdma_send_reply_msg(rdma, rdma_argp, rdma_resp, rqstp,
svc_rdma_sync_reply_hdr(rdma, sctxt, svc_rdma_reply_hdr_len(rdma_resp));
ret = svc_rdma_send_reply_msg(rdma, sctxt, rdma_argp, rqstp,
wr_lst, rp_ch);
if (ret < 0)
goto err0;
goto err1;
ret = 0;
out:
@ -820,14 +823,14 @@ out:
if (ret != -E2BIG && ret != -EINVAL)
goto err1;
ret = svc_rdma_send_error_msg(rdma, rdma_resp, rqstp);
ret = svc_rdma_send_error_msg(rdma, sctxt, rqstp);
if (ret < 0)
goto err0;
goto err1;
ret = 0;
goto out;
err1:
put_page(res_page);
svc_rdma_send_ctxt_put(rdma, sctxt);
err0:
trace_svcrdma_send_failed(rqstp, ret);
set_bit(XPT_CLOSE, &xprt->xpt_flags);