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

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Message-ID: <f0e91dbf-8379-f481-0009-1f19c79a610d@bytedance.com>
Date:   Fri, 14 Oct 2022 10:02:10 +0800
From:   Chengming Zhou <zhouchengming@...edance.com>
To:     Johannes Weiner <hannes@...xchg.org>
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 2022/10/13 23:52, Johannes Weiner wrote:
> 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.

Ok, will move these resched logic to the end of get_recent_times().

> 
>> @@ -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?

Yes, only psi_avgs_work() use this to re-arm now, I will add this check next version.

Thanks.