On Tue, Dec 21, 2021 at 3:58 AM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > On Fri, Dec 17, 2021 at 10:03 PM Zhaoyang Huang <huangzhaoyang@xxxxxxxxx> wrote: > > > > loop Suren > > Thanks. > > > > > > On Fri, Dec 17, 2021 at 2:08 PM Huangzhaoyang <huangzhaoyang@xxxxxxxxx> wrote: > > > > > > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> > > > > > > There could be missing wake up if the rest of the window remain the > > > same stall states as the polling_total updates for every polling_min_period. > > Could you please expand on this description? I'm unclear what the > problem is. I assume "polling_min_period" in this description refers > to the group->poll_min_period. > > From the code, looks like the change results in update_triggers() > calling window_update() once there was a new stall recorded for the > trigger state and until the tracking window is complete. I don't see > the point of calling window_update() if there was no stall change > since the last call to window_update(). The resulting growth will not > increase if there is no new stall. > Maybe what you want to achieve here is more than one trigger per > window if the stall limit was breached? If so, then this goes against > the design for psi triggers in which we want to rate-limit the number > of generated triggers per tracking window (see: > https://elixir.bootlin.com/linux/latest/source/kernel/sched/psi.c#L545). > Please clarify the issue and the intentions here. > Thanks! Please correct me if I am wrong. Imagine that there is a new stall during the 1st polling_min_period among 10 of them in the window and group->polling_total will be updated to total without trigger. If the rest of 9 polling_min_periods remain the same states, the trigger will be missed when window timing is reached. > > > > > > > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> > > > --- > > > include/linux/psi_types.h | 2 ++ > > > kernel/sched/psi.c | 30 ++++++++++++++++++------------ > > > 2 files changed, 20 insertions(+), 12 deletions(-) > > > > > > diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h > > > index 0a23300..9533d2e 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 new_stall; > > > }; > > > > > > struct psi_group { > > > diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c > > > index 1652f2b..402718c 100644 > > > --- a/kernel/sched/psi.c > > > +++ b/kernel/sched/psi.c > > > @@ -458,9 +458,12 @@ static void psi_avgs_work(struct work_struct *work) > > > static void window_reset(struct psi_window *win, u64 now, u64 value, > > > u64 prev_growth) > > > { > > > + struct psi_trigger *t = container_of(win, struct psi_trigger, win); > > > + > > > win->start_time = now; > > > win->start_value = value; > > > win->prev_growth = prev_growth; > > > + t->new_stall = false; > > > } > > > > > > /* > > > @@ -515,7 +518,6 @@ 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; > > > u64 *total = group->total[PSI_POLL]; > > > > > > /* > > > @@ -523,19 +525,26 @@ static u64 update_triggers(struct psi_group *group, u64 now) > > > * watchers know when their specified thresholds are exceeded. > > > */ > > > list_for_each_entry(t, &group->triggers, node) { > > > - u64 growth; > > > - > > > /* 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. > > > + * update the trigger if there is new stall which will be > > > + * reset when run out of the window > > > */ > > > - new_stall = true; > > > + t->new_stall = true; > > > + > > > + memcpy(&group->polling_total[t->state], &total[t->state], > > > + sizeof(group->polling_total[t->state])); > > > + } > > > + > > > + list_for_each_entry(t, &group->triggers, node) { > > > + u64 growth; > > > + > > > + /* check if new stall happened during this window*/ > > > + if (!t->new_stall) > > > + continue; > > > > > > /* Calculate growth since last update */ > > > growth = window_update(&t->win, now, total[t->state]); > > > @@ -552,10 +561,6 @@ static u64 update_triggers(struct psi_group *group, u64 now) > > > t->last_event_time = now; > > > } > > > > > > - if (new_stall) > > > - memcpy(group->polling_total, total, > > > - sizeof(group->polling_total)); > > > - > > > return now + group->poll_min_period; > > > } > > > > > > @@ -1152,6 +1157,7 @@ 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->new_stall = false; > > > > > > mutex_lock(&group->trigger_lock); > > > > > > -- > > > 1.9.1 > > >
