From 9ef33ef5b628037b694a433f8af014a04bb38126 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Wed, 19 Jun 2019 10:33:26 -0400 Subject: [PATCH] xprtrdma: Streamline rpcrdma_post_recvs rb_lock is contended between rpcrdma_buffer_create, rpcrdma_buffer_put, and rpcrdma_post_recvs. Commit e340c2d6ef2a ("xprtrdma: Reduce the doorbell rate (Receive)") causes rpcrdma_post_recvs to take the rb_lock repeatedly when it determines more Receives are needed. Streamline this code path so it takes the lock just once in most cases to build the Receive chain that is about to be posted. Signed-off-by: Chuck Lever Signed-off-by: Anna Schumaker --- net/sunrpc/xprtrdma/verbs.c | 59 ++++++++++++++++++++++++------------- 1 file changed, 38 insertions(+), 21 deletions(-) diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c index de6be101abf2..3270c8ad1819 100644 --- a/net/sunrpc/xprtrdma/verbs.c +++ b/net/sunrpc/xprtrdma/verbs.c @@ -1478,11 +1478,13 @@ rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, bool temp) { struct rpcrdma_buffer *buf = &r_xprt->rx_buf; struct rpcrdma_ep *ep = &r_xprt->rx_ep; - struct ib_recv_wr *wr, *bad_wr; + struct ib_recv_wr *i, *wr, *bad_wr; + struct rpcrdma_rep *rep; int needed, count, rc; rc = 0; count = 0; + needed = buf->rb_credits + (buf->rb_bc_srv_max_requests << 1); if (ep->rep_receive_count > needed) goto out; @@ -1490,39 +1492,48 @@ rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, bool temp) if (!temp) needed += RPCRDMA_MAX_RECV_BATCH; - count = 0; + /* fast path: all needed reps can be found on the free list */ wr = NULL; + spin_lock(&buf->rb_lock); while (needed) { - struct rpcrdma_rep *rep; - - spin_lock(&buf->rb_lock); rep = list_first_entry_or_null(&buf->rb_recv_bufs, struct rpcrdma_rep, rr_list); - if (likely(rep)) - list_del(&rep->rr_list); - spin_unlock(&buf->rb_lock); - if (!rep) { - rep = rpcrdma_rep_create(r_xprt, temp); - if (!rep) - break; - } + if (!rep) + break; - if (!rpcrdma_regbuf_dma_map(r_xprt, rep->rr_rdmabuf)) { - rpcrdma_recv_buffer_put(rep); + list_del(&rep->rr_list); + rep->rr_recv_wr.next = wr; + wr = &rep->rr_recv_wr; + --needed; + } + spin_unlock(&buf->rb_lock); + + while (needed) { + rep = rpcrdma_rep_create(r_xprt, temp); + if (!rep) break; - } - trace_xprtrdma_post_recv(rep->rr_recv_wr.wr_cqe); rep->rr_recv_wr.next = wr; wr = &rep->rr_recv_wr; - ++count; --needed; } - if (!count) + if (!wr) goto out; + for (i = wr; i; i = i->next) { + rep = container_of(i, struct rpcrdma_rep, rr_recv_wr); + + if (!rpcrdma_regbuf_dma_map(r_xprt, rep->rr_rdmabuf)) + goto release_wrs; + + trace_xprtrdma_post_recv(rep->rr_recv_wr.wr_cqe); + ++count; + } + rc = ib_post_recv(r_xprt->rx_ia.ri_id->qp, wr, (const struct ib_recv_wr **)&bad_wr); +out: + trace_xprtrdma_post_recvs(r_xprt, count, rc); if (rc) { for (wr = bad_wr; wr;) { struct rpcrdma_rep *rep; @@ -1534,6 +1545,12 @@ rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, bool temp) } } ep->rep_receive_count += count; -out: - trace_xprtrdma_post_recvs(r_xprt, count, rc); + return; + +release_wrs: + for (i = wr; i;) { + rep = container_of(i, struct rpcrdma_rep, rr_recv_wr); + i = i->next; + rpcrdma_recv_buffer_put(rep); + } } -- 2.45.2