diff options
author | Chuck Lever <chuck.lever@oracle.com> | 2019-06-19 17:33:10 +0300 |
---|---|---|
committer | Anna Schumaker <Anna.Schumaker@Netapp.com> | 2019-07-09 17:30:25 +0300 |
commit | d8099feda4833bab96b1bf312e9e6aad6b771570 (patch) | |
tree | ec6af94bc83c935b9a7ad96819184990ed97da92 /net/sunrpc/xprtrdma/frwr_ops.c | |
parent | 40088f0e9b62d7fa033918b54ef45f8bf7d1ad1c (diff) | |
download | linux-d8099feda4833bab96b1bf312e9e6aad6b771570.tar.xz |
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 <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Diffstat (limited to 'net/sunrpc/xprtrdma/frwr_ops.c')
-rw-r--r-- | net/sunrpc/xprtrdma/frwr_ops.c | 103 |
1 files changed, 102 insertions, 1 deletions
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); +} |