Since commit ba69cd122ece ("xprtrdma: Remove support for FMR memory
registration"), FRWR is the only supported memory registration mode.
We can take advantage of the asynchronous nature of FRWR's LOCAL_INV
Work Requests to get rid of the completion wait by having the
LOCAL_INV completion handler take care of DMA unmapping MRs and
waking the upper layer RPC waiter.
This eliminates two context switches when local invalidation is
necessary. As a side benefit, we will no longer need the per-xprt
deferred completion work queue.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
include/trace/events/rpcrdma.h | 1
net/sunrpc/xprtrdma/frwr_ops.c | 104 ++++++++++++++++++++++++++++++++++++++-
net/sunrpc/xprtrdma/rpc_rdma.c | 61 +++++++++++------------
net/sunrpc/xprtrdma/verbs.c | 17 ------
net/sunrpc/xprtrdma/xprt_rdma.h | 8 ++-
5 files changed, 136 insertions(+), 55 deletions(-)
diff --git a/include/trace/events/rpcrdma.h b/include/trace/events/rpcrdma.h
index 7fe21ba..eadcd09 100644
--- a/include/trace/events/rpcrdma.h
+++ b/include/trace/events/rpcrdma.h
@@ -710,6 +710,7 @@
DEFINE_FRWR_DONE_EVENT(xprtrdma_wc_fastreg);
DEFINE_FRWR_DONE_EVENT(xprtrdma_wc_li);
DEFINE_FRWR_DONE_EVENT(xprtrdma_wc_li_wake);
+DEFINE_FRWR_DONE_EVENT(xprtrdma_wc_li_done);
TRACE_EVENT(xprtrdma_frwr_alloc,
TP_PROTO(
diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index ae97119..e5500f7 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -546,7 +546,10 @@ static void frwr_wc_localinv_wake(struct ib_cq *cq, struct ib_wc *wc)
* @req: rpcrdma_req with a non-empty list of MRs to process
*
* Sleeps until it is safe for the host CPU to access the previously mapped
- * memory regions.
+ * memory regions. This guarantees that registered MRs are properly fenced
+ * from the server before the RPC consumer accesses the data in them. It
+ * also ensures proper Send flow control: waking the next RPC waits until
+ * this RPC has relinquished all its Send Queue entries.
*/
void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
{
@@ -607,8 +610,7 @@ void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
if (!rc)
return;
- /* Unmap and release the MRs in the LOCAL_INV WRs that did not
- * get posted.
+ /* Recycle MRs in the LOCAL_INV chain that did not get posted.
*/
while (bad_wr) {
frwr = container_of(bad_wr, struct rpcrdma_frwr,
@@ -620,3 +622,99 @@ void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
rpcrdma_mr_recycle(mr);
}
}
+
+/**
+ * frwr_wc_localinv_done - Invoked by RDMA provider for a signaled LOCAL_INV WC
+ * @cq: completion queue (ignored)
+ * @wc: completed WR
+ *
+ */
+static void frwr_wc_localinv_done(struct ib_cq *cq, struct ib_wc *wc)
+{
+ struct ib_cqe *cqe = wc->wr_cqe;
+ struct rpcrdma_frwr *frwr =
+ container_of(cqe, struct rpcrdma_frwr, fr_cqe);
+ struct rpcrdma_mr *mr = container_of(frwr, struct rpcrdma_mr, frwr);
+
+ /* WARNING: Only wr_cqe and status are reliable at this point */
+ __frwr_release_mr(wc, mr);
+ trace_xprtrdma_wc_li_done(wc, frwr);
+ rpcrdma_complete_rqst(frwr->fr_req->rl_reply);
+}
+
+/**
+ * frwr_unmap_async - invalidate memory regions that were registered for @req
+ * @r_xprt: controlling transport instance
+ * @req: rpcrdma_req with a non-empty list of MRs to process
+ *
+ * This guarantees that registered MRs are properly fenced from the
+ * server before the RPC consumer accesses the data in them. It also
+ * ensures proper Send flow control: waking the next RPC waits until
+ * this RPC has relinquished all its Send Queue entries.
+ */
+void frwr_unmap_async(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
+{
+ struct ib_send_wr *first, *last, **prev;
+ const struct ib_send_wr *bad_wr;
+ struct rpcrdma_frwr *frwr;
+ struct rpcrdma_mr *mr;
+ int rc;
+
+ /* Chain the LOCAL_INV Work Requests and post them with
+ * a single ib_post_send() call.
+ */
+ prev = &first;
+ while (!list_empty(&req->rl_registered)) {
+ mr = rpcrdma_mr_pop(&req->rl_registered);
+
+ trace_xprtrdma_mr_localinv(mr);
+ r_xprt->rx_stats.local_inv_needed++;
+
+ frwr = &mr->frwr;
+ frwr->fr_cqe.done = frwr_wc_localinv;
+ frwr->fr_req = req;
+ last = &frwr->fr_invwr;
+ last->next = NULL;
+ last->wr_cqe = &frwr->fr_cqe;
+ last->sg_list = NULL;
+ last->num_sge = 0;
+ last->opcode = IB_WR_LOCAL_INV;
+ last->send_flags = IB_SEND_SIGNALED;
+ last->ex.invalidate_rkey = mr->mr_handle;
+
+ *prev = last;
+ prev = &last->next;
+ }
+
+ /* Strong send queue ordering guarantees that when the
+ * last WR in the chain completes, all WRs in the chain
+ * are complete.
+ */
+ frwr->fr_cqe.done = frwr_wc_localinv_done;
+
+ /* Transport disconnect drains the receive CQ before it
+ * replaces the QP. The RPC reply handler won't call us
+ * unless ri_id->qp is a valid pointer.
+ */
+ bad_wr = NULL;
+ rc = ib_post_send(r_xprt->rx_ia.ri_id->qp, first, &bad_wr);
+ trace_xprtrdma_post_send(req, rc);
+ if (!rc)
+ return;
+
+ /* Recycle MRs in the LOCAL_INV chain that did not get posted.
+ */
+ while (bad_wr) {
+ frwr = container_of(bad_wr, struct rpcrdma_frwr, fr_invwr);
+ mr = container_of(frwr, struct rpcrdma_mr, frwr);
+ bad_wr = bad_wr->next;
+
+ rpcrdma_mr_recycle(mr);
+ }
+
+ /* The final LOCAL_INV WR in the chain is supposed to
+ * do the wake. If it never gets posted, the wake will
+ * not happen, so wake here in that case.
+ */
+ rpcrdma_complete_rqst(req->rl_reply);
+}
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index f211f81..ea39f74 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -1268,24 +1268,15 @@ void rpcrdma_complete_rqst(struct rpcrdma_rep *rep)
goto out;
}
-void rpcrdma_release_rqst(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
+/* Ensure that any DMA mapped pages associated with
+ * the Send of the RPC Call have been unmapped before
+ * allowing the RPC to complete. This protects argument
+ * memory not controlled by the RPC client from being
+ * re-used before we're done with it.
+ */
+static void rpcrdma_release_tx(struct rpcrdma_xprt *r_xprt,
+ struct rpcrdma_req *req)
{
- /* Invalidate and unmap the data payloads before waking
- * the waiting application. This guarantees the memory
- * regions are properly fenced from the server before the
- * application accesses the data. It also ensures proper
- * send flow control: waking the next RPC waits until this
- * RPC has relinquished all its Send Queue entries.
- */
- if (!list_empty(&req->rl_registered))
- frwr_unmap_sync(r_xprt, req);
-
- /* Ensure that any DMA mapped pages associated with
- * the Send of the RPC Call have been unmapped before
- * allowing the RPC to complete. This protects argument
- * memory not controlled by the RPC client from being
- * re-used before we're done with it.
- */
if (test_bit(RPCRDMA_REQ_F_TX_RESOURCES, &req->rl_flags)) {
r_xprt->rx_stats.reply_waits_for_send++;
out_of_line_wait_on_bit(&req->rl_flags,
@@ -1295,24 +1286,23 @@ void rpcrdma_release_rqst(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
}
}
-/* Reply handling runs in the poll worker thread. Anything that
- * might wait is deferred to a separate workqueue.
+/**
+ * rpcrdma_release_rqst - Release hardware resources
+ * @r_xprt: controlling transport instance
+ * @req: request with resources to release
+ *
*/
-void rpcrdma_deferred_completion(struct work_struct *work)
+void rpcrdma_release_rqst(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
{
- struct rpcrdma_rep *rep =
- container_of(work, struct rpcrdma_rep, rr_work);
- struct rpcrdma_req *req = rpcr_to_rdmar(rep->rr_rqst);
- struct rpcrdma_xprt *r_xprt = rep->rr_rxprt;
+ if (!list_empty(&req->rl_registered))
+ frwr_unmap_sync(r_xprt, req);
- trace_xprtrdma_defer_cmp(rep);
- if (rep->rr_wc_flags & IB_WC_WITH_INVALIDATE)
- frwr_reminv(rep, &req->rl_registered);
- rpcrdma_release_rqst(r_xprt, req);
- rpcrdma_complete_rqst(rep);
+ rpcrdma_release_tx(r_xprt, req);
}
-/* Process received RPC/RDMA messages.
+/**
+ * rpcrdma_reply_handler - Process received RPC/RDMA messages
+ * @rep: Incoming rpcrdma_rep object to process
*
* Errors must result in the RPC task either being awakened, or
* allowed to timeout, to discover the errors at that time.
@@ -1374,7 +1364,16 @@ void rpcrdma_reply_handler(struct rpcrdma_rep *rep)
rep->rr_rqst = rqst;
trace_xprtrdma_reply(rqst->rq_task, rep, req, credits);
- queue_work(buf->rb_completion_wq, &rep->rr_work);
+
+ if (rep->rr_wc_flags & IB_WC_WITH_INVALIDATE)
+ frwr_reminv(rep, &req->rl_registered);
+ if (!list_empty(&req->rl_registered)) {
+ frwr_unmap_async(r_xprt, req);
+ /* LocalInv completion will complete the RPC */
+ } else {
+ rpcrdma_release_tx(r_xprt, req);
+ rpcrdma_complete_rqst(rep);
+ }
return;
out_badversion:
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 78be985..0be455b 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -89,14 +89,12 @@
*/
static void rpcrdma_xprt_drain(struct rpcrdma_xprt *r_xprt)
{
- struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
struct rpcrdma_ia *ia = &r_xprt->rx_ia;
/* Flush Receives, then wait for deferred Reply work
* to complete.
*/
ib_drain_rq(ia->ri_id->qp);
- drain_workqueue(buf->rb_completion_wq);
/* Deferred Reply processing might have scheduled
* local invalidations.
@@ -1057,7 +1055,6 @@ static bool rpcrdma_rep_create(struct rpcrdma_xprt *r_xprt, bool temp)
rep->rr_cqe.done = rpcrdma_wc_receive;
rep->rr_rxprt = r_xprt;
- INIT_WORK(&rep->rr_work, rpcrdma_deferred_completion);
rep->rr_recv_wr.next = NULL;
rep->rr_recv_wr.wr_cqe = &rep->rr_cqe;
rep->rr_recv_wr.sg_list = &rep->rr_rdmabuf->rg_iov;
@@ -1118,15 +1115,6 @@ int rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt)
if (rc)
goto out;
- buf->rb_completion_wq = alloc_workqueue("rpcrdma-%s",
- WQ_MEM_RECLAIM | WQ_HIGHPRI,
- 0,
- r_xprt->rx_xprt.address_strings[RPC_DISPLAY_ADDR]);
- if (!buf->rb_completion_wq) {
- rc = -ENOMEM;
- goto out;
- }
-
return 0;
out:
rpcrdma_buffer_destroy(buf);
@@ -1200,11 +1188,6 @@ static void rpcrdma_rep_destroy(struct rpcrdma_rep *rep)
{
cancel_delayed_work_sync(&buf->rb_refresh_worker);
- if (buf->rb_completion_wq) {
- destroy_workqueue(buf->rb_completion_wq);
- buf->rb_completion_wq = NULL;
- }
-
rpcrdma_sendctxs_destroy(buf);
while (!list_empty(&buf->rb_recv_bufs)) {
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index a396528..e465221 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -202,10 +202,9 @@ struct rpcrdma_rep {
bool rr_temp;
struct rpcrdma_regbuf *rr_rdmabuf;
struct rpcrdma_xprt *rr_rxprt;
- struct work_struct rr_work;
+ struct rpc_rqst *rr_rqst;
struct xdr_buf rr_hdrbuf;
struct xdr_stream rr_stream;
- struct rpc_rqst *rr_rqst;
struct list_head rr_list;
struct ib_recv_wr rr_recv_wr;
};
@@ -240,10 +239,12 @@ struct rpcrdma_sendctx {
* An external memory region is any buffer or page that is registered
* on the fly (ie, not pre-registered).
*/
+struct rpcrdma_req;
struct rpcrdma_frwr {
struct ib_mr *fr_mr;
struct ib_cqe fr_cqe;
struct completion fr_linv_done;
+ struct rpcrdma_req *fr_req;
union {
struct ib_reg_wr fr_regwr;
struct ib_send_wr fr_invwr;
@@ -388,7 +389,6 @@ struct rpcrdma_buffer {
u32 rb_bc_srv_max_requests;
u32 rb_bc_max_requests;
- struct workqueue_struct *rb_completion_wq;
struct delayed_work rb_refresh_worker;
};
@@ -561,6 +561,7 @@ struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
int frwr_send(struct rpcrdma_ia *ia, struct rpcrdma_req *req);
void frwr_reminv(struct rpcrdma_rep *rep, struct list_head *mrs);
void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req);
+void frwr_unmap_async(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req);
/*
* RPC/RDMA protocol calls - xprtrdma/rpc_rdma.c
@@ -585,7 +586,6 @@ int rpcrdma_prepare_send_sges(struct rpcrdma_xprt *r_xprt,
void rpcrdma_reply_handler(struct rpcrdma_rep *rep);
void rpcrdma_release_rqst(struct rpcrdma_xprt *r_xprt,
struct rpcrdma_req *req);
-void rpcrdma_deferred_completion(struct work_struct *work);
static inline void rpcrdma_set_xdrlen(struct xdr_buf *xdr, size_t len)
{
