From 0cdfb3b20797804ae835d7a325b08d8523794089 Mon Sep 17 00:00:00 2001 From: Md Haris Iqbal Date: Fri, 28 May 2021 13:30:11 +0200 Subject: [PATCH] RDMA/rtrs-srv: Replace atomic_t with percpu_ref for ids_inflight ids_inflight is used to track the inflight IOs. But the use of atomic_t variable can cause performance drops and can also become a performance bottleneck. This commit replaces the use of atomic_t with a percpu_ref structure. The advantage it offers is, it doesn't check if the reference has fallen to 0, until the user explicitly signals it to; and that is done by the percpu_ref_kill() function call. After that, the percpu_ref structure behaves like an atomic_t and for every put call, checks whether the reference has fallen to 0 or not. rtrs_srv_stats_rdma_to_str shows the count of ids_inflight as 0 for user-mode tools not to be confused. Fixes: 9cb837480424e ("RDMA/rtrs: server: main functionality") Link: https://lore.kernel.org/r/20210528113018.52290-14-jinpu.wang@ionos.com Signed-off-by: Md Haris Iqbal Signed-off-by: Jack Wang Signed-off-by: Gioh Kim Signed-off-by: Jason Gunthorpe --- drivers/infiniband/ulp/rtrs/rtrs-srv-stats.c | 12 ++++---- drivers/infiniband/ulp/rtrs/rtrs-srv.c | 43 ++++++++++++++++++---------- drivers/infiniband/ulp/rtrs/rtrs-srv.h | 4 +-- 3 files changed, 35 insertions(+), 24 deletions(-) diff --git a/drivers/infiniband/ulp/rtrs/rtrs-srv-stats.c b/drivers/infiniband/ulp/rtrs/rtrs-srv-stats.c index e102b13..520c247 100644 --- a/drivers/infiniband/ulp/rtrs/rtrs-srv-stats.c +++ b/drivers/infiniband/ulp/rtrs/rtrs-srv-stats.c @@ -27,12 +27,10 @@ ssize_t rtrs_srv_stats_rdma_to_str(struct rtrs_srv_stats *stats, char *page, size_t len) { struct rtrs_srv_stats_rdma_stats *r = &stats->rdma_stats; - struct rtrs_srv_sess *sess = stats->sess; - return scnprintf(page, len, "%lld %lld %lld %lld %u\n", - (s64)atomic64_read(&r->dir[READ].cnt), - (s64)atomic64_read(&r->dir[READ].size_total), - (s64)atomic64_read(&r->dir[WRITE].cnt), - (s64)atomic64_read(&r->dir[WRITE].size_total), - atomic_read(&sess->ids_inflight)); + return scnprintf(page, len, "%lld %lld %lld %lldn %u\n", + (s64)atomic64_read(&r->dir[READ].cnt), + (s64)atomic64_read(&r->dir[READ].size_total), + (s64)atomic64_read(&r->dir[WRITE].cnt), + (s64)atomic64_read(&r->dir[WRITE].size_total), 0); } diff --git a/drivers/infiniband/ulp/rtrs/rtrs-srv.c b/drivers/infiniband/ulp/rtrs/rtrs-srv.c index 840a342..631d379 100644 --- a/drivers/infiniband/ulp/rtrs/rtrs-srv.c +++ b/drivers/infiniband/ulp/rtrs/rtrs-srv.c @@ -111,7 +111,6 @@ static void rtrs_srv_free_ops_ids(struct rtrs_srv_sess *sess) struct rtrs_srv *srv = sess->srv; int i; - WARN_ON(atomic_read(&sess->ids_inflight)); if (sess->ops_ids) { for (i = 0; i < srv->queue_depth; i++) free_id(sess->ops_ids[i]); @@ -126,11 +125,19 @@ static struct ib_cqe io_comp_cqe = { .done = rtrs_srv_rdma_done }; +static inline void rtrs_srv_inflight_ref_release(struct percpu_ref *ref) +{ + struct rtrs_srv_sess *sess = container_of(ref, struct rtrs_srv_sess, ids_inflight_ref); + + percpu_ref_exit(&sess->ids_inflight_ref); + complete(&sess->complete_done); +} + static int rtrs_srv_alloc_ops_ids(struct rtrs_srv_sess *sess) { struct rtrs_srv *srv = sess->srv; struct rtrs_srv_op *id; - int i; + int i, ret; sess->ops_ids = kcalloc(srv->queue_depth, sizeof(*sess->ops_ids), GFP_KERNEL); @@ -144,8 +151,14 @@ static int rtrs_srv_alloc_ops_ids(struct rtrs_srv_sess *sess) sess->ops_ids[i] = id; } - init_waitqueue_head(&sess->ids_waitq); - atomic_set(&sess->ids_inflight, 0); + + ret = percpu_ref_init(&sess->ids_inflight_ref, + rtrs_srv_inflight_ref_release, 0, GFP_KERNEL); + if (ret) { + pr_err("Percpu reference init failed\n"); + goto err; + } + init_completion(&sess->complete_done); return 0; @@ -156,21 +169,14 @@ err: static inline void rtrs_srv_get_ops_ids(struct rtrs_srv_sess *sess) { - atomic_inc(&sess->ids_inflight); + percpu_ref_get(&sess->ids_inflight_ref); } static inline void rtrs_srv_put_ops_ids(struct rtrs_srv_sess *sess) { - if (atomic_dec_and_test(&sess->ids_inflight)) - wake_up(&sess->ids_waitq); + percpu_ref_put(&sess->ids_inflight_ref); } -static void rtrs_srv_wait_ops_ids(struct rtrs_srv_sess *sess) -{ - wait_event(sess->ids_waitq, !atomic_read(&sess->ids_inflight)); -} - - static void rtrs_srv_reg_mr_done(struct ib_cq *cq, struct ib_wc *wc) { struct rtrs_srv_con *con = to_srv_con(wc->qp->qp_context); @@ -1479,8 +1485,15 @@ static void rtrs_srv_close_work(struct work_struct *work) rdma_disconnect(con->c.cm_id); ib_drain_qp(con->c.qp); } - /* Wait for all inflights */ - rtrs_srv_wait_ops_ids(sess); + + /* + * Degrade ref count to the usual model with a single shared + * atomic_t counter + */ + percpu_ref_kill(&sess->ids_inflight_ref); + + /* Wait for all completion */ + wait_for_completion(&sess->complete_done); /* Notify upper layer if we are the last path */ rtrs_srv_sess_down(sess); diff --git a/drivers/infiniband/ulp/rtrs/rtrs-srv.h b/drivers/infiniband/ulp/rtrs/rtrs-srv.h index 9543ae1..f8da2e3 100644 --- a/drivers/infiniband/ulp/rtrs/rtrs-srv.h +++ b/drivers/infiniband/ulp/rtrs/rtrs-srv.h @@ -81,8 +81,8 @@ struct rtrs_srv_sess { spinlock_t state_lock; int cur_cq_vector; struct rtrs_srv_op **ops_ids; - atomic_t ids_inflight; - wait_queue_head_t ids_waitq; + struct percpu_ref ids_inflight_ref; + struct completion complete_done; struct rtrs_srv_mr *mrs; unsigned int mrs_num; dma_addr_t *dma_addr; -- 2.7.4