sched/psi: Avoid resetting the min update period when it is unnecessary

Psi_group's poll_min_period is determined by the minimum window size of
psi_trigger when creating new triggers. While destroying a psi_trigger,
there is no need to reset poll_min_period if the psi_trigger being
destroyed did not have the minimum window size, since in this condition
poll_min_period will remain the same as before.

Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Link: https://lkml.kernel.org/r/20230514163338.834345-1-surenb@google.com

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index b49af594ad283022e481bec920fb73ef57ce8bdf..81fca77397f6a2f194dccb26a02d361579de8bea 100644 (file)
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -1407,11 +1407,16 @@ void psi_trigger_destroy(struct psi_trigger *t)
                        group->rtpoll_nr_triggers[t->state]--;
                        if (!group->rtpoll_nr_triggers[t->state])
                                group->rtpoll_states &= ~(1 << t->state);
-                       /* reset min update period for the remaining triggers */
-                       list_for_each_entry(tmp, &group->rtpoll_triggers, node)
-                               period = min(period, div_u64(tmp->win.size,
-                                               UPDATES_PER_WINDOW));
-                       group->rtpoll_min_period = period;
+                       /*
+                        * Reset min update period for the remaining triggers
+                        * iff the destroying trigger had the min window size.
+                        */
+                       if (group->rtpoll_min_period == div_u64(t->win.size, UPDATES_PER_WINDOW)) {
+                               list_for_each_entry(tmp, &group->rtpoll_triggers, node)
+                                       period = min(period, div_u64(tmp->win.size,
+                                                       UPDATES_PER_WINDOW));
+                               group->rtpoll_min_period = period;
+                       }
                        /* Destroy rtpoll_task when the last trigger is destroyed */
                        if (group->rtpoll_states == 0) {
                                group->rtpoll_until = 0;