Re: [PATCH v2] sched/fair: Sync se's load_avg with cfs_rq in reweight_task

[Chuyi Zhou]

-------- 转发的消息 --------
主题: Re: [PATCH v2] sched/fair: Sync se's load_avg with cfs_rq in 
reweight_task
日期: Mon, 29 Jul 2024 11:06:33 +0800
From: Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx>
收件人: Qais Yousef <qyousef@xxxxxxxxxxx>, K Prateek Nayak 
<kprateek.nayak@xxxxxxx>
抄送: mingo@xxxxxxxxxx, peterz@xxxxxxxxxxxxx, juri.lelli@xxxxxxxxxx, 
vincent.guittot@xxxxxxxxxx, dietmar.eggemann@xxxxxxx, 
rostedt@xxxxxxxxxxx, bsegall@xxxxxxxxxx, mgorman@xxxxxxx, 
vschneid@xxxxxxxxxx, chengming.zhou@xxxxxxxxx

Hello Qais,

在 2024/7/29 04:14, Qais Yousef 写道:
> On 07/22/24 10:47, K Prateek Nayak wrote:
> > (+ Qais)
> >
> > Hello Chuyi,
> >
> > On 7/20/2024 10:42 AM, Chuyi Zhou wrote:
> > > In reweight_task(), there are two situations:
> > >
> > > 1. The task was on_rq, then the task's load_avg is accurate because we
> > > synchronized it with cfs_rq through update_load_avg() in dequeue_task().
> > >
> > > 2. The task is sleeping, its load_avg might not have been updated for some
> > > time, which can result in inaccurate dequeue_load_avg() in
> > > reweight_entity().
> > >
> > > This patch solves this by using update_load_avg() to synchronize the
> > > load_avg of se with cfs_rq. For tasks were on_rq, since we already update
> > > load_avg to accurate values in dequeue_task(), this change will not have
> > > other effects due to the short time interval between the two updates.
> > >
> > > Signed-off-by: Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx>
> > > ---
> > > Changes in v2:
> > > - change the description in commit log.
> > > - use update_load_avg() in reweight_task() rather than in reweight_entity
> > > suggested by chengming.
> > > - Link to v1: https://lore.kernel.org/lkml/20240716150840.23061-1-zhouchuyi@xxxxxxxxxxxxx/
> > > ---
> > >    kernel/sched/fair.c | 3 +++
> > >    1 file changed, 3 insertions(+)
> > >
> > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > > index 9057584ec06d..b1e07ce90284 100644
> > > --- a/kernel/sched/fair.c
> > > +++ b/kernel/sched/fair.c
> > > @@ -3835,12 +3835,15 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
> > >    	}
> > >    }
> > > +static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags);
> > > +
> > >    void reweight_task(struct task_struct *p, const struct load_weight *lw)
> > >    {
> > >    	struct sched_entity *se = &p->se;
> > >    	struct cfs_rq *cfs_rq = cfs_rq_of(se);
> > >    	struct load_weight *load = &se->load;
> > > +	update_load_avg(cfs_rq, se, 0);
>
> White space and a comment perhaps?
>
> LGTM anyway.

Thanks for taking a look, will send another patch later.

(V3 
link:https://lore.kernel.org/lkml/20240723114247.104848-1-zhouchuyi@xxxxxxxxxxxxx/)