Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-ie0-f176.google.com ([209.85.223.176]:37735 "EHLO mail-ie0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752119AbbAMQZv (ORCPT ); Tue, 13 Jan 2015 11:25:51 -0500 Subject: [PATCH v2 08/20] xprtrdma: Move credit update to RPC reply handler From: Chuck Lever To: linux-rdma@vger.kernel.org, linux-nfs@vger.kernel.org Date: Tue, 13 Jan 2015 11:25:49 -0500 Message-ID: <20150113162549.14086.21319.stgit@manet.1015granger.net> In-Reply-To: <20150113161440.14086.24801.stgit@manet.1015granger.net> References: <20150113161440.14086.24801.stgit@manet.1015granger.net> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Sender: linux-nfs-owner@vger.kernel.org List-ID: Reduce work in the receive CQ handler, which is run at hardware interrupt level, by moving the RPC/RDMA credit update logic to the RPC reply handler. This has some additional benefits: More header sanity checking is done before trusting the incoming credit value, and the receive CQ handler no longer touches the RPC/RDMA header. Finally, no longer any need to update and read rb_credits atomically, so the rb_credits field can be removed. This further extends work begun by commit e7ce710a8802 ("xprtrdma: Avoid deadlock when credit window is reset"). Signed-off-by: Chuck Lever --- net/sunrpc/xprtrdma/rpc_rdma.c | 10 ++++++++-- net/sunrpc/xprtrdma/verbs.c | 15 ++------------- net/sunrpc/xprtrdma/xprt_rdma.h | 1 - 3 files changed, 10 insertions(+), 16 deletions(-) diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c index dcf5ebc..d731010 100644 --- a/net/sunrpc/xprtrdma/rpc_rdma.c +++ b/net/sunrpc/xprtrdma/rpc_rdma.c @@ -736,7 +736,7 @@ rpcrdma_reply_handler(struct rpcrdma_rep *rep) struct rpc_xprt *xprt = rep->rr_xprt; struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt); __be32 *iptr; - int rdmalen, status; + int credits, rdmalen, status; unsigned long cwnd; /* Check status. If bad, signal disconnect and return rep to pool */ @@ -871,8 +871,14 @@ badheader: break; } + credits = be32_to_cpu(headerp->rm_credit); + if (credits == 0) + credits = 1; /* don't deadlock */ + else if (credits > r_xprt->rx_buf.rb_max_requests) + credits = r_xprt->rx_buf.rb_max_requests; + cwnd = xprt->cwnd; - xprt->cwnd = atomic_read(&r_xprt->rx_buf.rb_credits) << RPC_CWNDSHIFT; + xprt->cwnd = credits << RPC_CWNDSHIFT; if (xprt->cwnd > cwnd) xprt_release_rqst_cong(rqst->rq_task); diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c index 1000f63..71a071a 100644 --- a/net/sunrpc/xprtrdma/verbs.c +++ b/net/sunrpc/xprtrdma/verbs.c @@ -49,6 +49,7 @@ #include #include +#include #include #include "xprt_rdma.h" @@ -298,17 +299,7 @@ rpcrdma_recvcq_process_wc(struct ib_wc *wc, struct list_head *sched_list) rep->rr_len = wc->byte_len; ib_dma_sync_single_for_cpu(rdmab_to_ia(rep->rr_buffer)->ri_id->device, rep->rr_iov.addr, rep->rr_len, DMA_FROM_DEVICE); - - if (rep->rr_len >= 16) { - struct rpcrdma_msg *p = (struct rpcrdma_msg *)rep->rr_base; - unsigned int credits = ntohl(p->rm_credit); - - if (credits == 0) - credits = 1; /* don't deadlock */ - else if (credits > rep->rr_buffer->rb_max_requests) - credits = rep->rr_buffer->rb_max_requests; - atomic_set(&rep->rr_buffer->rb_credits, credits); - } + prefetch(rep->rr_base); out_schedule: list_add_tail(&rep->rr_list, sched_list); @@ -480,7 +471,6 @@ rpcrdma_conn_upcall(struct rdma_cm_id *id, struct rdma_cm_event *event) case RDMA_CM_EVENT_DEVICE_REMOVAL: connstate = -ENODEV; connected: - atomic_set(&rpcx_to_rdmax(ep->rep_xprt)->rx_buf.rb_credits, 1); dprintk("RPC: %s: %sconnected\n", __func__, connstate > 0 ? "" : "dis"); ep->rep_connected = connstate; @@ -1186,7 +1176,6 @@ rpcrdma_buffer_create(struct rpcrdma_buffer *buf, struct rpcrdma_ep *ep, buf->rb_max_requests = cdata->max_requests; spin_lock_init(&buf->rb_lock); - atomic_set(&buf->rb_credits, 1); /* Need to allocate: * 1. arrays for send and recv pointers diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h index 532d586..3fcc92b 100644 --- a/net/sunrpc/xprtrdma/xprt_rdma.h +++ b/net/sunrpc/xprtrdma/xprt_rdma.h @@ -248,7 +248,6 @@ struct rpcrdma_req { */ struct rpcrdma_buffer { spinlock_t rb_lock; /* protects indexes */ - atomic_t rb_credits; /* most recent server credits */ int rb_max_requests;/* client max requests */ struct list_head rb_mws; /* optional memory windows/fmrs/frmrs */ struct list_head rb_all;