| Message ID | 1640132668-28249-1-git-send-email-huangzhaoyang@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] psi: fix possible trigger missing in the window | expand |
On Tue, Dec 21, 2021 at 4:24 PM Huangzhaoyang <huangzhaoyang@gmail.com> wrote: > > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com> Please remember to CC Peter. > > 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> > --- > 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 >
@Peter Zijlstra @Johannes Weiner Would you please review this patch? We would like to have it be merged ASAP. Thanks. On Wed, Dec 22, 2021 at 8:31 AM Suren Baghdasaryan <surenb@google.com> wrote: > > On Tue, Dec 21, 2021 at 4:24 PM Huangzhaoyang <huangzhaoyang@gmail.com> wrote: > > > > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com> > > Please remember to CC Peter. > > > > > 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> > > --- > > 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 > >
On Wed, Dec 22, 2021 at 4:50 PM Zhaoyang Huang <huangzhaoyang@gmail.com> wrote: > > @Peter Zijlstra @Johannes Weiner > Would you please review this patch? We would like to have it be merged > ASAP. Thanks. It's the holiday season, so I would not expect a quick turnaround. > > On Wed, Dec 22, 2021 at 8:31 AM Suren Baghdasaryan <surenb@google.com> wrote: > > > > On Tue, Dec 21, 2021 at 4:24 PM Huangzhaoyang <huangzhaoyang@gmail.com> wrote: > > > > > > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com> > > > > Please remember to CC Peter. > > > > > > > > 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> > > > --- > > > 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 > > >
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);