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authorGerd Rausch <gerd.rausch@oracle.com>2019-06-29 03:31:19 +0300
committerSantosh Shilimkar <santosh.shilimkar@oracle.com>2019-07-10 07:45:41 +0300
commita55207884708bf1d5b8c87a3c504502de77a5416 (patch)
tree65b06062d9c6f97fc55c68d15abfc63bc18106a8 /net/rds/ib_cm.c
parent616d37a070bb33ea387d0e93343acd8336a30886 (diff)
downloadlinux-a55207884708bf1d5b8c87a3c504502de77a5416.tar.xz
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 <gerd.rausch@oracle.com> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Diffstat (limited to 'net/rds/ib_cm.c')
-rw-r--r--net/rds/ib_cm.c9
1 files changed, 2 insertions, 7 deletions
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);