From a55207884708bf1d5b8c87a3c504502de77a5416 Mon Sep 17 00:00:00 2001 From: Gerd Rausch Date: Fri, 28 Jun 2019 17:31:19 -0700 Subject: Revert "RDS: IB: split the mr registration and invalidation path" This reverts commit 56012459310a1dbcc55c2dbf5500a9f7571402cb. RDS kept spinning inside function "rds_ib_post_reg_frmr", waiting for "i_fastreg_wrs" to become incremented: while (atomic_dec_return(&ibmr->ic->i_fastreg_wrs) <= 0) { atomic_inc(&ibmr->ic->i_fastreg_wrs); cpu_relax(); } Looking at the original commit: commit 56012459310a ("RDS: IB: split the mr registration and invalidation path") In there, the "rds_ib_mr_cqe_handler" was changed in the following way: void rds_ib_mr_cqe_handler(struct rds_ib_connection *ic, struct ib_wc *wc) if (frmr->fr_inv) { frmr->fr_state = FRMR_IS_FREE; frmr->fr_inv = false; atomic_inc(&ic->i_fastreg_wrs); } else { atomic_inc(&ic->i_fastunreg_wrs); } It looks like it's got it exactly backwards: Function "rds_ib_post_reg_frmr" keeps track of the outstanding requests via "i_fastreg_wrs". Function "rds_ib_post_inv" keeps track of the outstanding requests via "i_fastunreg_wrs" (post original commit). It also sets: frmr->fr_inv = true; However the completion handler "rds_ib_mr_cqe_handler" adjusts "i_fastreg_wrs" when "fr_inv" had been true, and adjusts "i_fastunreg_wrs" otherwise. The original commit was done in the name of performance: to remove the performance bottleneck No performance benefit could be observed with a fixed-up version of the original commit measured between two Oracle X7 servers, both equipped with Mellanox Connect-X5 HCAs. The prudent course of action is to revert this commit. Signed-off-by: Gerd Rausch Signed-off-by: Santosh Shilimkar --- net/rds/ib_cm.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) (limited to 'net/rds/ib_cm.c') diff --git a/net/rds/ib_cm.c b/net/rds/ib_cm.c index 66c6eb56072b..8891822eba4f 100644 --- a/net/rds/ib_cm.c +++ b/net/rds/ib_cm.c @@ -460,10 +460,7 @@ static int rds_ib_setup_qp(struct rds_connection *conn) * completion queue and send queue. This extra space is used for FRMR * registration and invalidation work requests */ - fr_queue_space = rds_ibdev->use_fastreg ? - (RDS_IB_DEFAULT_FR_WR + 1) + - (RDS_IB_DEFAULT_FR_INV_WR + 1) - : 0; + fr_queue_space = (rds_ibdev->use_fastreg ? RDS_IB_DEFAULT_FR_WR : 0); /* add the conn now so that connection establishment has the dev */ rds_ib_add_conn(rds_ibdev, conn); @@ -530,7 +527,6 @@ static int rds_ib_setup_qp(struct rds_connection *conn) attr.send_cq = ic->i_send_cq; attr.recv_cq = ic->i_recv_cq; atomic_set(&ic->i_fastreg_wrs, RDS_IB_DEFAULT_FR_WR); - atomic_set(&ic->i_fastunreg_wrs, RDS_IB_DEFAULT_FR_INV_WR); /* * XXX this can fail if max_*_wr is too large? Are we supposed @@ -1009,8 +1005,7 @@ void rds_ib_conn_path_shutdown(struct rds_conn_path *cp) wait_event(rds_ib_ring_empty_wait, rds_ib_ring_empty(&ic->i_recv_ring) && (atomic_read(&ic->i_signaled_sends) == 0) && - (atomic_read(&ic->i_fastreg_wrs) == RDS_IB_DEFAULT_FR_WR) && - (atomic_read(&ic->i_fastunreg_wrs) == RDS_IB_DEFAULT_FR_INV_WR)); + (atomic_read(&ic->i_fastreg_wrs) == RDS_IB_DEFAULT_FR_WR)); tasklet_kill(&ic->i_send_tasklet); tasklet_kill(&ic->i_recv_tasklet); -- cgit v1.2.3-59-g8ed1b