The RPC-over-RDMA version 1 remote invalidation extension requires
the server to select the R_key to invalidate. Make two minor
optimizations to the selection algorithm:
o Select the R_key to invalidate while the CPU cache still contains
the received RPC Call transport header, rather than waiting until
we're about to send the RPC Reply.
o Choose Send With Invalidate if there is exactly one distinct R_key
in the received transport header.
The reason for the second change:
Remote invalidation can invalidate only a single R_key. If the RPC
has multiple R_keys, the Receive completion will wait for the
remote invalidation, and then the RPC completion will wait for the
local invalidations. Waiting twice takes longer.
This change improves the throughput of large I/Os by a few percent,
and has no effect on smaller I/Os.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
Hi Bruce-
This is ready for your for-next branch.
Changes since v2:
- Rebased on v4.20-rc6
- Further clarify the patch description
include/linux/sunrpc/svc_rdma.h | 1
net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 63 +++++++++++++++++++++++++++++++
net/sunrpc/xprtrdma/svc_rdma_sendto.c | 53 ++++++--------------------
3 files changed, 77 insertions(+), 40 deletions(-)
diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index e6e2691..7e22681 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -135,6 +135,7 @@ struct svc_rdma_recv_ctxt {
u32 rc_byte_len;
unsigned int rc_page_count;
unsigned int rc_hdr_count;
+ u32 rc_inv_rkey;
struct page *rc_pages[RPCSVC_MAXPAGES];
};
diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index b24d5b8..828b149 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -485,6 +485,68 @@ static __be32 *xdr_check_reply_chunk(__be32 *p, const __be32 *end)
return p;
}
+/* RPC-over-RDMA Version One private extension: Remote Invalidation.
+ * Responder's choice: requester signals it can handle Send With
+ * Invalidate, and responder chooses one R_key to invalidate.
+ *
+ * If there is exactly one distinct R_key in the received transport
+ * header, set rc_inv_rkey to that R_key. Otherwise, set it to zero.
+ *
+ * Perform this operation while the received transport header is
+ * still in the CPU cache.
+ */
+static void svc_rdma_get_inv_rkey(struct svcxprt_rdma *rdma,
+ struct svc_rdma_recv_ctxt *ctxt)
+{
+ __be32 inv_rkey, *p;
+ u32 i, segcount;
+
+ ctxt->rc_inv_rkey = 0;
+
+ if (!rdma->sc_snd_w_inv)
+ return;
+
+ inv_rkey = xdr_zero;
+ p = ctxt->rc_recv_buf;
+ p += rpcrdma_fixed_maxsz;
+
+ /* Read list */
+ while (*p++ != xdr_zero) {
+ p++; /* position */
+ if (inv_rkey == xdr_zero)
+ inv_rkey = *p;
+ else if (inv_rkey != *p)
+ return;
+ p += 4;
+ }
+
+ /* Write list */
+ while (*p++ != xdr_zero) {
+ segcount = be32_to_cpup(p++);
+ for (i = 0; i < segcount; i++) {
+ if (inv_rkey == xdr_zero)
+ inv_rkey = *p;
+ else if (inv_rkey != *p)
+ return;
+ p += 4;
+ }
+ }
+
+ /* Reply chunk */
+ if (*p++ != xdr_zero) {
+ segcount = be32_to_cpup(p++);
+ for (i = 0; i < segcount; i++) {
+ if (inv_rkey == xdr_zero)
+ inv_rkey = *p;
+ else if (inv_rkey != *p)
+ return;
+ p += 4;
+ }
+ }
+
+ ctxt->rc_inv_rkey = be32_to_cpu(inv_rkey);
+}
+
/* On entry, xdr->head[0].iov_base points to first byte in the
* RPC-over-RDMA header.
*
@@ -746,6 +808,7 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
return ret;
}
+ svc_rdma_get_inv_rkey(rdma_xprt, ctxt);
p += rpcrdma_fixed_maxsz;
if (*p != xdr_zero)
diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index 8602a5f..d48bc6d 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -484,32 +484,6 @@ static void svc_rdma_get_write_arrays(__be32 *rdma_argp,
*reply = NULL;
}
-/* RPC-over-RDMA Version One private extension: Remote Invalidation.
- * Responder's choice: requester signals it can handle Send With
- * Invalidate, and responder chooses one rkey to invalidate.
- *
- * Find a candidate rkey to invalidate when sending a reply. Picks the
- * first R_key it finds in the chunk lists.
- *
- * Returns zero if RPC's chunk lists are empty.
- */
-static u32 svc_rdma_get_inv_rkey(__be32 *rdma_argp,
- __be32 *wr_lst, __be32 *rp_ch)
-{
- __be32 *p;
-
- p = rdma_argp + rpcrdma_fixed_maxsz;
- if (*p != xdr_zero)
- p += 2;
- else if (wr_lst && be32_to_cpup(wr_lst + 1))
- p = wr_lst + 2;
- else if (rp_ch && be32_to_cpup(rp_ch + 1))
- p = rp_ch + 2;
- else
- return 0;
- return be32_to_cpup(p);
-}
-
static int svc_rdma_dma_map_page(struct svcxprt_rdma *rdma,
struct svc_rdma_send_ctxt *ctxt,
struct page *page,
@@ -672,7 +646,7 @@ static void svc_rdma_save_io_pages(struct svc_rqst *rqstp,
*
* RDMA Send is the last step of transmitting an RPC reply. Pages
* involved in the earlier RDMA Writes are here transferred out
- * of the rqstp and into the ctxt's page array. These pages are
+ * of the rqstp and into the sctxt's page array. These pages are
* DMA unmapped by each Write completion, but the subsequent Send
* completion finally releases these pages.
*
@@ -680,32 +654,31 @@ 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,
- struct svc_rdma_send_ctxt *ctxt,
- __be32 *rdma_argp,
+ struct svc_rdma_send_ctxt *sctxt,
+ struct svc_rdma_recv_ctxt *rctxt,
struct svc_rqst *rqstp,
__be32 *wr_lst, __be32 *rp_ch)
{
int ret;
if (!rp_ch) {
- ret = svc_rdma_map_reply_msg(rdma, ctxt,
+ ret = svc_rdma_map_reply_msg(rdma, sctxt,
&rqstp->rq_res, wr_lst);
if (ret < 0)
return ret;
}
- svc_rdma_save_io_pages(rqstp, ctxt);
+ svc_rdma_save_io_pages(rqstp, sctxt);
- ctxt->sc_send_wr.opcode = IB_WR_SEND;
- if (rdma->sc_snd_w_inv) {
- ctxt->sc_send_wr.ex.invalidate_rkey =
- svc_rdma_get_inv_rkey(rdma_argp, wr_lst, rp_ch);
- if (ctxt->sc_send_wr.ex.invalidate_rkey)
- ctxt->sc_send_wr.opcode = IB_WR_SEND_WITH_INV;
+ if (rctxt->rc_inv_rkey) {
+ sctxt->sc_send_wr.opcode = IB_WR_SEND_WITH_INV;
+ sctxt->sc_send_wr.ex.invalidate_rkey = rctxt->rc_inv_rkey;
+ } else {
+ sctxt->sc_send_wr.opcode = IB_WR_SEND;
}
dprintk("svcrdma: posting Send WR with %u sge(s)\n",
- ctxt->sc_send_wr.num_sge);
- return svc_rdma_send(rdma, &ctxt->sc_send_wr);
+ sctxt->sc_send_wr.num_sge);
+ return svc_rdma_send(rdma, &sctxt->sc_send_wr);
}
/* Given the client-provided Write and Reply chunks, the server was not
@@ -809,7 +782,7 @@ int svc_rdma_sendto(struct svc_rqst *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,
+ ret = svc_rdma_send_reply_msg(rdma, sctxt, rctxt, rqstp,
wr_lst, rp_ch);
if (ret < 0)
goto err1;
