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_frmr.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) (limited to 'net/rds/ib_frmr.c') diff --git a/net/rds/ib_frmr.c b/net/rds/ib_frmr.c index 688dcd68d4ea..32ae26ed58a0 100644 --- a/net/rds/ib_frmr.c +++ b/net/rds/ib_frmr.c @@ -239,8 +239,8 @@ static int rds_ib_post_inv(struct rds_ib_mr *ibmr) if (frmr->fr_state != FRMR_IS_INUSE) goto out; - while (atomic_dec_return(&ibmr->ic->i_fastunreg_wrs) <= 0) { - atomic_inc(&ibmr->ic->i_fastunreg_wrs); + while (atomic_dec_return(&ibmr->ic->i_fastreg_wrs) <= 0) { + atomic_inc(&ibmr->ic->i_fastreg_wrs); cpu_relax(); } @@ -257,7 +257,7 @@ static int rds_ib_post_inv(struct rds_ib_mr *ibmr) if (unlikely(ret)) { frmr->fr_state = FRMR_IS_STALE; frmr->fr_inv = false; - atomic_inc(&ibmr->ic->i_fastunreg_wrs); + atomic_inc(&ibmr->ic->i_fastreg_wrs); pr_err("RDS/IB: %s returned error(%d)\n", __func__, ret); goto out; } @@ -285,10 +285,9 @@ 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); } + + atomic_inc(&ic->i_fastreg_wrs); } void rds_ib_unreg_frmr(struct list_head *list, unsigned int *nfreed, -- cgit v1.2.3