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authorZhaoyang Huang <zhaoyang.huang@unisoc.com>2022-01-25 14:56:58 +0800
committerPeter Zijlstra <peterz@infradead.org>2022-02-16 15:57:54 +0100
commite6df4ead85d9da1b07dd40bd4c6d2182f3e210c4 (patch)
tree1af29301a0595cc3d539c7927b31d41e6a5812ce /kernel/sched
parent5c7b1aaf139dab5072311853bacc40fc3457d1f9 (diff)
psi: fix possible trigger missing in the window
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@google.com> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Suren Baghdasaryan <surenb@google.com> Link: https://lore.kernel.org/r/1643093818-19835-1-git-send-email-huangzhaoyang@gmail.com
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/psi.c46
1 files changed, 30 insertions, 16 deletions
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index cfe76f704d8a..e9d623cb8d1b 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -523,7 +523,7 @@ static void init_triggers(struct psi_group *group, u64 now)
static u64 update_triggers(struct psi_group *group, u64 now)
{
struct psi_trigger *t;
- bool new_stall = false;
+ bool update_total = false;
u64 *total = group->total[PSI_POLL];
/*
@@ -532,24 +532,35 @@ static u64 update_triggers(struct psi_group *group, u64 now)
*/
list_for_each_entry(t, &group->triggers, node) {
u64 growth;
+ bool new_stall;
- /* Check for stall activity */
- if (group->polling_total[t->state] == total[t->state])
- continue;
+ new_stall = group->polling_total[t->state] != total[t->state];
+ /* Check for stall activity or a previous threshold breach */
+ if (!new_stall && !t->pending_event)
+ 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.
+ * Check for new stall activity, as well as deferred
+ * events that occurred in the last window after the
+ * trigger had already fired (we want to ratelimit
+ * events without dropping any).
*/
- new_stall = true;
-
- /* Calculate growth since last update */
- growth = window_update(&t->win, now, total[t->state]);
- if (growth < t->threshold)
- continue;
-
+ if (new_stall) {
+ /*
+ * 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.
+ */
+ update_total = true;
+
+ /* Calculate growth since last update */
+ growth = window_update(&t->win, now, total[t->state]);
+ if (growth < t->threshold)
+ continue;
+
+ t->pending_event = true;
+ }
/* Limit event signaling to once per window */
if (now < t->last_event_time + t->win.size)
continue;
@@ -558,9 +569,11 @@ 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->pending_event = false;
}
- if (new_stall)
+ if (update_total)
memcpy(group->polling_total, total,
sizeof(group->polling_total));
@@ -1125,6 +1138,7 @@ 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->pending_event = false;
mutex_lock(&group->trigger_lock);