From d8099feda4833bab96b1bf312e9e6aad6b771570 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Wed, 19 Jun 2019 10:33:10 -0400 Subject: [PATCH] xprtrdma: Reduce context switching due to Local Invalidation 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 Signed-off-by: Anna Schumaker --- include/trace/events/rpcrdma.h | 1 + net/sunrpc/xprtrdma/frwr_ops.c | 103 +++++++++++++++++++++++++++++++- net/sunrpc/xprtrdma/rpc_rdma.c | 61 ++++++++++--------- net/sunrpc/xprtrdma/verbs.c | 17 ------ net/sunrpc/xprtrdma/xprt_rdma.h | 8 +-- 5 files changed, 137 insertions(+), 53 deletions(-) diff --git a/include/trace/events/rpcrdma.h b/include/trace/events/rpcrdma.h index 1d2547084998..98023d91a72d 100644 --- a/include/trace/events/rpcrdma.h +++ b/include/trace/events/rpcrdma.h @@ -712,6 +712,7 @@ TRACE_EVENT(xprtrdma_wc_receive, 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 524cac0a0715..0b6dad7580a1 100644 --- a/net/sunrpc/xprtrdma/frwr_ops.c +++ b/net/sunrpc/xprtrdma/frwr_ops.c @@ -542,7 +542,10 @@ 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) { @@ -616,3 +619,101 @@ 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 */ + trace_xprtrdma_wc_li_done(wc, frwr); + rpcrdma_complete_rqst(frwr->fr_req->rl_reply); + __frwr_release_mr(wc, mr); +} + +/** + * 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. + */ + frwr = NULL; + 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. The last completion will wake up the + * RPC waiter. + */ + 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 was never 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 67d72d68ca6c..33b6e6a03f68 100644 --- a/net/sunrpc/xprtrdma/rpc_rdma.c +++ b/net/sunrpc/xprtrdma/rpc_rdma.c @@ -1268,24 +1268,15 @@ out_badheader: 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 0be5a36cacb6..c50a4b295bd7 100644 --- a/net/sunrpc/xprtrdma/verbs.c +++ b/net/sunrpc/xprtrdma/verbs.c @@ -89,14 +89,12 @@ static void rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, bool temp); */ 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. @@ -1056,7 +1054,6 @@ 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; @@ -1117,15 +1114,6 @@ 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); @@ -1199,11 +1187,6 @@ rpcrdma_buffer_destroy(struct rpcrdma_buffer *buf) { 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 a39652884308..e465221c9c96 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 @@ void rpcrdma_complete_rqst(struct rpcrdma_rep *rep); 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) {