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Subject[PATCH 1/1] sched/psi: avoid resetting the min update period when it is unnecessary
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From: Yang Yang <yang.yang29@zte.com.cn>

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>
Acked-by: Suren Baghdasaryan <surenb@google.com>
---
rebase of https://lore.kernel.org/all/202305121642367753446@zte.com.cn/
over git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched/core branch

kernel/sched/psi.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index b49af594ad28..81fca77397f6 100644
--- 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;
--
2.40.1.606.ga4b1b128d6-goog
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