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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
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25
net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
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@@ -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);