From: Md Haris Iqbal <haris.iqbal@xxxxxxxxxxxxxxx>
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")
Signed-off-by: Md Haris Iqbal <haris.iqbal@xxxxxxxxx>
Signed-off-by: Jack Wang <jinpu.wang@xxxxxxxxx>
Signed-off-by: Gioh Kim <gi-oh.kim@xxxxxxxxx>
---
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 e102b1368d0c..df1d7d6b1884 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 sysfs_emit(page, "%lld %lld %lld %lldn\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));
}
diff --git a/drivers/infiniband/ulp/rtrs/rtrs-srv.c b/drivers/infiniband/ulp/rtrs/rtrs-srv.c
index 54a29285240d..f66f2be9f519 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 @@ static int rtrs_srv_alloc_ops_ids(struct rtrs_srv_sess *sess)
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 9543ae19996c..f8da2e3f0bda 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;
--
2.25.1
