Re: [PATCH] RFC: sched: Rework task_sched_runtime to avoid calling update_rq_clock

[Qais Yousef <qyousef@layalina.io>]

On 06/13/24 12:04, Peter Zijlstra wrote:

> ---
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 0935f9d4bb7b..d4b87539d72a 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -724,7 +724,6 @@ static void update_rq_clock_task(struct rq *rq, s64 delta)
>  
>  	rq->prev_irq_time += irq_delta;
>  	delta -= irq_delta;
> -	psi_account_irqtime(rq->curr, irq_delta);
>  	delayacct_irq(rq->curr, irq_delta);
>  #endif
>  #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
> @@ -5459,6 +5458,8 @@ void sched_tick(void)
>  
>  	sched_clock_tick();
>  
> +	psi_account_irqtime(curr, &rq->psi_irq_time);
> +

If wakeup preemption causes a context switch, wouldn't we lose this
information then? I *think* active migration might cause this information to be
lost too.

pick_next_task() might be a better place to do the accounting?

>  	rq_lock(rq, &rf);
>  
>  	update_rq_clock(rq);