From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
When a new threshold breaching stall happens after a psi event was
generated and within the window duration, the new event is not
generated because the events are rate-limited to one per window. If
after that no new stall is recorded then the event will not be
generated even after rate-limiting duration has passed. This is
happening because with no new stall, window_update will not be called
even though threshold was previously breached. To fix this, record
threshold breaching occurrence and generate the event once window
duration is passed.
Suggested-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
v2: modify the logic according to Suren's suggestion
v3: update commit message
---
---
include/linux/psi_types.h | 2 ++
kernel/sched/psi.c | 38 +++++++++++++++++++++++---------------
2 files changed, 25 insertions(+), 15 deletions(-)
diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h
index 0a23300..87b694a 100644
--- a/include/linux/psi_types.h
+++ b/include/linux/psi_types.h
@@ -132,6 +132,8 @@ struct psi_trigger {
/* Refcounting to prevent premature destruction */
struct kref refcount;
+
+ bool threshold_breach;
};
struct psi_group {
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 1652f2b..5c67ab9 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -524,24 +524,29 @@ static u64 update_triggers(struct psi_group *group, u64 now)
*/
list_for_each_entry(t, &group->triggers, node) {
u64 growth;
+ bool trigger_stalled =
+ group->polling_total[t->state] != total[t->state];
- /* Check for stall activity */
- if (group->polling_total[t->state] == total[t->state])
- continue;
-
- /*
- * Multiple triggers might be looking at the same state,
- * remember to update group->polling_total[] once we've
- * been through all of them. Also remember to extend the
- * polling time if we see new stall activity.
- */
- new_stall = true;
-
- /* Calculate growth since last update */
- growth = window_update(&t->win, now, total[t->state]);
- if (growth < t->threshold)
+ /* Check for stall activity or a previous threshold breach */
+ if (!trigger_stalled && !t->threshold_breach)
continue;
+ if (trigger_stalled) {
+ /*
+ * Multiple triggers might be looking at the same state,
+ * remember to update group->polling_total[] once we've
+ * been through all of them. Also remember to extend the
+ * polling time if we see new stall activity.
+ */
+ new_stall = true;
+
+ /* Calculate growth since last update */
+ growth = window_update(&t->win, now, total[t->state]);
+ if (growth < t->threshold)
+ continue;
+
+ t->threshold_breach = true;
+ }
/* Limit event signaling to once per window */
if (now < t->last_event_time + t->win.size)
continue;
@@ -550,6 +555,8 @@ static u64 update_triggers(struct psi_group *group, u64 now)
if (cmpxchg(&t->event, 0, 1) == 0)
wake_up_interruptible(&t->event_wait);
t->last_event_time = now;
+ /* Reset threshold breach flag once event got generated */
+ t->threshold_breach = false;
}
if (new_stall)
@@ -1152,6 +1159,7 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group,
t->last_event_time = 0;
init_waitqueue_head(&t->event_wait);
kref_init(&t->refcount);
+ t->threshold_breach = false;
mutex_lock(&group->trigger_lock);
--
1.9.1
