Hello,
Thanks for picking this up. There is a newer version which has been acked:
https://lore.kernel.org/all/20221014110551.22695-1-zhouchengming@xxxxxxxxxxxxx/
As well another PSI patch that has been acked by Johannes:
https://lore.kernel.org/all/20220926081931.45420-1-zhouchengming@xxxxxxxxxxxxx/
Thanks!
On 2022/10/28 14:42, tip-bot2 for Chengming Zhou wrote:
> The following commit has been merged into the sched/core branch of tip:
>
> Commit-ID: 7d89d7bb921c5ae5a428df282e64ee5692e26fe0
> Gitweb: https://git.kernel.org/tip/7d89d7bb921c5ae5a428df282e64ee5692e26fe0
> Author: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
> AuthorDate: Mon, 10 Oct 2022 18:42:06 +08:00
> Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> CommitterDate: Thu, 27 Oct 2022 11:01:23 +02:00
>
> sched/psi: Fix avgs_work re-arm in psi_avgs_work()
>
> Pavan reported a problem that PSI avgs_work idle shutoff is not
> working at all. Because PSI_NONIDLE condition would be observed in
> psi_avgs_work()->collect_percpu_times()->get_recent_times() even if
> only the kworker running avgs_work on the CPU.
>
> Although commit 1b69ac6b40eb ("psi: fix aggregation idle shut-off")
> avoided the ping-pong wake problem when the worker sleep, psi_avgs_work()
> still will always re-arm the avgs_work, so shutoff is not working.
>
> This patch changes to consider current CPU groupc as IDLE if the
> kworker running avgs_work is the only task running and no IOWAIT
> or MEMSTALL sleep tasks, in which case we will shut off the avgs_work
> if other CPUs' groupc are also IDLE.
>
> One potential problem is that the brief period of non-idle time
> incurred between the aggregation run and the kworker's dequeue will
> be stranded in the per-cpu buckets until avgs_work run next time.
> The buckets can hold 4s worth of time, and future activity will wake
> the avgs_work with a 2s delay, giving us 2s worth of data we can leave
> behind when shut off the avgs_work. If the kworker run other works after
> avgs_work shut off and doesn't have any scheduler activities for 2s,
> this maybe a problem.
>
> Reported-by: Pavan Kondeti <quic_pkondeti@xxxxxxxxxxx>
> Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Link: https://lore.kernel.org/r/20221010104206.12184-1-zhouchengming@xxxxxxxxxxxxx
> ---
> kernel/sched/psi.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index ee2ecc0..f4cdf6f 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -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 only_avgs_work = false;
> u64 now, state_start;
> enum psi_states s;
> unsigned int seq;
> @@ -256,6 +258,15 @@ 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;
> + /*
> + * This CPU has only avgs_work kworker running, snapshot the
> + * newest times then don't need to re-arm for this groupc.
> + * Normally this kworker will sleep soon and won't wake
> + * avgs_work back up in psi_group_change().
> + */
> + if (current_cpu == cpu && groupc->tasks[NR_RUNNING] == 1 &&
> + !groupc->tasks[NR_IOWAIT] && !groupc->tasks[NR_MEMSTALL])
> + only_avgs_work = true;
> } while (read_seqcount_retry(&groupc->seq, seq));
>
> /* Calculate state time deltas against the previous snapshot */
> @@ -280,6 +291,10 @@ static void get_recent_times(struct psi_group *group, int cpu,
> if (delta)
> *pchanged_states |= (1 << s);
> }
> +
> + /* Clear PSI_NONIDLE so avgs_work won't be re-armed for this groupc */
> + if (only_avgs_work)
> + *pchanged_states &= ~(1 << PSI_NONIDLE);
> }
>
> static void calc_avgs(unsigned long avg[3], int missed_periods,
|