linux-kernel - Re: [PATCH] sched/psi: Fix avgs_work re-arm in psi_avgs

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Message-ID: <Y0g0UAAJMhPczNm/@cmpxchg.org>
Date:   Thu, 13 Oct 2022 11:52:48 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Chengming Zhou <zhouchengming@...edance.com>
Cc:     Suren Baghdasaryan <surenb@...gle.com>, quic_pkondeti@...cinc.com,
        peterz@...radead.org, quic_charante@...cinc.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/psi: Fix avgs_work re-arm in psi_avgs_work()

On Thu, Oct 13, 2022 at 07:06:55PM +0800, Chengming Zhou wrote:
> Should I still need to copy groupc->tasks[] out for the current_cpu as you
> suggested before?

It'd be my preference as well. This way the resched logic can be
consolidated into a single block of comment + code at the end of the
function.

> @@ -242,6 +242,8 @@ static void get_recent_times(struct psi_group *group, int cpu,
>                              u32 *pchanged_states)
>  {
>         struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
> +       int current_cpu = raw_smp_processor_id();
> +       bool reschedule;
>         u64 now, state_start;
>         enum psi_states s;
>         unsigned int seq;
> @@ -256,6 +258,10 @@ static void get_recent_times(struct psi_group *group, int cpu,
>                 memcpy(times, groupc->times, sizeof(groupc->times));
>                 state_mask = groupc->state_mask;
>                 state_start = groupc->state_start;
> +               if (cpu == current_cpu)
> +                       reschedule = groupc->tasks[NR_RUNNING] +
> +                               groupc->tasks[NR_IOWAIT] +
> +                               groupc->tasks[NR_MEMSTALL] > 1;
>         } while (read_seqcount_retry(&groupc->seq, seq));

This also matches psi_show() and the poll worker. They don't currently
use the flag, but it's somewhat fragile and confusing. Add a test for
current_work() == &group->avgs_work?