Re: [PATCH] psi : calc cfs task memstall time more precisely

[Johannes Weiner]

Please don't send new revisions without replying to previous feedback.

On Fri, Sep 10, 2021 at 03:54:46PM +0800, Huangzhaoyang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> 
> cfs task's memstall time is counted as simple as exit - entry so far, which
> ignore the preempted time by rt, dl and irq time. Eliminating them by calc the
> time growth via the proportion of cfs_rq's utilization on the whole rq.
> 
> eg.
> Here is the scenario which this commit want to fix, that is the rt and irq consume
> some utilization of the whole rq. This scenario could be typical in a core
> which is assigned to deal with all irqs. Furthermore, the rt task used to run on
> little core under EAS.
> 
> Binder:305_3-314    [002] d..1   257.880195: psi_memtime_fixup: original:30616,adjusted:25951,se:89,cfs:353,rt:139,dl:0,irq:18
> droid.phone-1525    [001] d..1   265.145492: psi_memtime_fixup: original:61616,adjusted:53492,se:55,cfs:225,rt:121,dl:0,irq:15
> 
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> ---
>  kernel/sched/psi.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index cc25a3c..754a836 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -182,6 +182,8 @@ struct psi_group psi_system = {
>  
>  static void psi_avgs_work(struct work_struct *work);
>  
> +static unsigned long psi_memtime_fixup(u32 growth);
> +
>  static void group_init(struct psi_group *group)
>  {
>  	int cpu;
> @@ -492,6 +494,21 @@ static u64 window_update(struct psi_window *win, u64 now, u64 value)
>  	return growth;
>  }
>  
> +static unsigned long psi_memtime_fixup(u32 growth)
> +{
> +	struct rq *rq = task_rq(current);
> +	unsigned long growth_fixed = (unsigned long)growth;
> +
> +	if (!(current->policy == SCHED_NORMAL || current->policy == SCHED_BATCH))
> +		return growth_fixed;
> +
> +	if (current->in_memstall)
> +		growth_fixed = div64_ul((1024 - rq->avg_rt.util_avg - rq->avg_dl.util_avg
> +					- rq->avg_irq.util_avg + 1) * growth, 1024);
> +
> +	return growth_fixed;
> +}
> +
>  static void init_triggers(struct psi_group *group, u64 now)
>  {
>  	struct psi_trigger *t;
> @@ -658,6 +675,7 @@ static void record_times(struct psi_group_cpu *groupc, u64 now)
>  	}
>  
>  	if (groupc->state_mask & (1 << PSI_MEM_SOME)) {
> +		delta = psi_memtime_fixup(delta);
>  		groupc->times[PSI_MEM_SOME] += delta;
>  		if (groupc->state_mask & (1 << PSI_MEM_FULL))
>  			groupc->times[PSI_MEM_FULL] += delta;
> @@ -928,8 +946,8 @@ void psi_memstall_leave(unsigned long *flags)
>  	 */
>  	rq = this_rq_lock_irq(&rf);
>  
> -	current->in_memstall = 0;
>  	psi_task_change(current, TSK_MEMSTALL, 0);
> +	current->in_memstall = 0;
>  
>  	rq_unlock_irq(rq, &rf);
>  }
> -- 
> 1.9.1
>