xprtrdma: Wake RPCs directly in rpcrdma_wc_send path
Eliminate a context switch in the path that handles RPC wake-ups when a Receive completion has to wait for a Send completion. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
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0ab1152370
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@ -511,6 +511,16 @@ rpcrdma_encode_reply_chunk(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
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return 0;
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}
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static void rpcrdma_sendctx_done(struct kref *kref)
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{
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struct rpcrdma_req *req =
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container_of(kref, struct rpcrdma_req, rl_kref);
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struct rpcrdma_rep *rep = req->rl_reply;
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rpcrdma_complete_rqst(rep);
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rep->rr_rxprt->rx_stats.reply_waits_for_send++;
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}
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/**
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* rpcrdma_sendctx_unmap - DMA-unmap Send buffer
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* @sc: sendctx containing SGEs to unmap
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@ -520,6 +530,9 @@ void rpcrdma_sendctx_unmap(struct rpcrdma_sendctx *sc)
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{
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struct ib_sge *sge;
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if (!sc->sc_unmap_count)
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return;
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/* The first two SGEs contain the transport header and
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* the inline buffer. These are always left mapped so
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* they can be cheaply re-used.
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@ -529,9 +542,7 @@ void rpcrdma_sendctx_unmap(struct rpcrdma_sendctx *sc)
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ib_dma_unmap_page(sc->sc_device, sge->addr, sge->length,
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DMA_TO_DEVICE);
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if (test_and_clear_bit(RPCRDMA_REQ_F_TX_RESOURCES,
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&sc->sc_req->rl_flags))
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wake_up_bit(&sc->sc_req->rl_flags, RPCRDMA_REQ_F_TX_RESOURCES);
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kref_put(&sc->sc_req->rl_kref, rpcrdma_sendctx_done);
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}
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/* Prepare an SGE for the RPC-over-RDMA transport header.
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@ -666,7 +677,7 @@ map_tail:
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out:
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sc->sc_wr.num_sge += sge_no;
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if (sc->sc_unmap_count)
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__set_bit(RPCRDMA_REQ_F_TX_RESOURCES, &req->rl_flags);
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kref_get(&req->rl_kref);
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return true;
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out_regbuf:
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@ -708,7 +719,7 @@ rpcrdma_prepare_send_sges(struct rpcrdma_xprt *r_xprt,
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req->rl_sendctx->sc_wr.num_sge = 0;
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req->rl_sendctx->sc_unmap_count = 0;
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req->rl_sendctx->sc_req = req;
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__clear_bit(RPCRDMA_REQ_F_TX_RESOURCES, &req->rl_flags);
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kref_init(&req->rl_kref);
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ret = -EIO;
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if (!rpcrdma_prepare_hdr_sge(r_xprt, req, hdrlen))
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@ -1268,36 +1279,12 @@ out_badheader:
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goto out;
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}
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/* Ensure that any DMA mapped pages associated with
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* the Send of the RPC Call have been unmapped before
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* allowing the RPC to complete. This protects argument
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* memory not controlled by the RPC client from being
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* re-used before we're done with it.
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*/
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static void rpcrdma_release_tx(struct rpcrdma_xprt *r_xprt,
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struct rpcrdma_req *req)
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static void rpcrdma_reply_done(struct kref *kref)
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{
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if (test_bit(RPCRDMA_REQ_F_TX_RESOURCES, &req->rl_flags)) {
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r_xprt->rx_stats.reply_waits_for_send++;
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out_of_line_wait_on_bit(&req->rl_flags,
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RPCRDMA_REQ_F_TX_RESOURCES,
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bit_wait,
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TASK_UNINTERRUPTIBLE);
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}
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}
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struct rpcrdma_req *req =
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container_of(kref, struct rpcrdma_req, rl_kref);
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/**
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* rpcrdma_release_rqst - Release hardware resources
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* @r_xprt: controlling transport instance
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* @req: request with resources to release
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*
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*/
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void rpcrdma_release_rqst(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
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{
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if (!list_empty(&req->rl_registered))
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frwr_unmap_sync(r_xprt, req);
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rpcrdma_release_tx(r_xprt, req);
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rpcrdma_complete_rqst(req->rl_reply);
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}
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/**
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@ -1367,13 +1354,11 @@ void rpcrdma_reply_handler(struct rpcrdma_rep *rep)
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if (rep->rr_wc_flags & IB_WC_WITH_INVALIDATE)
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frwr_reminv(rep, &req->rl_registered);
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if (!list_empty(&req->rl_registered)) {
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if (!list_empty(&req->rl_registered))
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frwr_unmap_async(r_xprt, req);
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/* LocalInv completion will complete the RPC */
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} else {
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rpcrdma_release_tx(r_xprt, req);
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rpcrdma_complete_rqst(rep);
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}
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else
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kref_put(&req->rl_kref, rpcrdma_reply_done);
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return;
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out_badversion:
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@ -618,8 +618,16 @@ xprt_rdma_free(struct rpc_task *task)
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struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
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struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
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rpcrdma_release_rqst(r_xprt, req);
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trace_xprtrdma_op_free(task, req);
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if (!list_empty(&req->rl_registered))
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frwr_unmap_sync(r_xprt, req);
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/* XXX: If the RPC is completing because of a signal and
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* not because a reply was received, we ought to ensure
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* that the Send completion has fired, so that memory
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* involved with the Send is not still visible to the NIC.
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*/
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}
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/**
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@ -1462,8 +1462,7 @@ rpcrdma_ep_post(struct rpcrdma_ia *ia,
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struct ib_send_wr *send_wr = &req->rl_sendctx->sc_wr;
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int rc;
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if (!ep->rep_send_count ||
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test_bit(RPCRDMA_REQ_F_TX_RESOURCES, &req->rl_flags)) {
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if (!ep->rep_send_count || kref_read(&req->rl_kref) > 1) {
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send_wr->send_flags |= IB_SEND_SIGNALED;
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ep->rep_send_count = ep->rep_send_batch;
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} else {
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@ -44,7 +44,8 @@
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#include <linux/wait.h> /* wait_queue_head_t, etc */
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#include <linux/spinlock.h> /* spinlock_t, etc */
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#include <linux/atomic.h> /* atomic_t, etc */
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#include <linux/atomic.h> /* atomic_t, etc */
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#include <linux/kref.h> /* struct kref */
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#include <linux/workqueue.h> /* struct work_struct */
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#include <rdma/rdma_cm.h> /* RDMA connection api */
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@ -329,17 +330,12 @@ struct rpcrdma_req {
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struct rpcrdma_regbuf *rl_recvbuf; /* rq_rcv_buf */
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struct list_head rl_all;
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unsigned long rl_flags;
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struct kref rl_kref;
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struct list_head rl_registered; /* registered segments */
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struct rpcrdma_mr_seg rl_segments[RPCRDMA_MAX_SEGS];
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};
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/* rl_flags */
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enum {
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RPCRDMA_REQ_F_TX_RESOURCES,
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};
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static inline struct rpcrdma_req *
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rpcr_to_rdmar(const struct rpc_rqst *rqst)
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{
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@ -584,8 +580,6 @@ int rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst);
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void rpcrdma_set_max_header_sizes(struct rpcrdma_xprt *);
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void rpcrdma_complete_rqst(struct rpcrdma_rep *rep);
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void rpcrdma_reply_handler(struct rpcrdma_rep *rep);
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void rpcrdma_release_rqst(struct rpcrdma_xprt *r_xprt,
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struct rpcrdma_req *req);
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static inline void rpcrdma_set_xdrlen(struct xdr_buf *xdr, size_t len)
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{
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