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    Subject[tip: sched/core] sched/psi: Avoid updating PSI triggers and ->rtpoll_total when there are no state changes
    The following commit has been merged into the sched/core branch of tip:

    Commit-ID: 80cc1d1d5ee35701daf11725ce06d8a240588973
    Gitweb: https://git.kernel.org/tip/80cc1d1d5ee35701daf11725ce06d8a240588973
    Author: Yang Yang <yang.yang29@zte.com.cn>
    AuthorDate: Tue, 10 Oct 2023 16:41:07 +08:00
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitterDate: Wed, 11 Oct 2023 23:07:50 +02:00

    sched/psi: Avoid updating PSI triggers and ->rtpoll_total when there are no state changes

    When psimon wakes up and there are no state changes for ->rtpoll_states,
    it's unnecessary to update triggers and ->rtpoll_total because the pressures
    being monitored by the user have not changed.

    This will help to slightly reduce unnecessary computations of PSI.

    [ mingo: Changelog updates ]

    Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Suren Baghdasaryan <surenb@google.com>
    Cc: Peter Ziljstra <peterz@infradead.org>
    Link: https://lore.kernel.org/r/202310101641075436843@zte.com.cn
    ---
    kernel/sched/psi.c | 7 ++++---
    1 file changed, 4 insertions(+), 3 deletions(-)

    diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
    index be853f2..79f8db0 100644
    --- a/kernel/sched/psi.c
    +++ b/kernel/sched/psi.c
    @@ -704,11 +704,12 @@ static void psi_rtpoll_work(struct psi_group *group)
    }

    if (now >= group->rtpoll_next_update) {
    - update_triggers(group, now, &update_total, PSI_POLL);
    - group->rtpoll_next_update = now + group->rtpoll_min_period;
    - if (update_total)
    + if (changed_states & group->rtpoll_states) {
    + update_triggers(group, now, &update_total, PSI_POLL);
    memcpy(group->rtpoll_total, group->total[PSI_POLL],
    sizeof(group->rtpoll_total));
    + }
    + group->rtpoll_next_update = now + group->rtpoll_min_period;
    }

    psi_schedule_rtpoll_work(group,
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