linux-kernel - Re: [PATCH] sched/rt: Rework for_each_process_thread() iterations in tg_has_rt

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Date:   Fri, 20 Apr 2018 12:58:52 +0200
From:   Juri Lelli <juri.lelli@...il.com>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     mingo@...hat.com, peterz@...radead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/rt: Rework for_each_process_thread() iterations in
 tg_has_rt_tasks()

On 20/04/18 12:43, Kirill Tkhai wrote:
> On 20.04.2018 12:25, Juri Lelli wrote:

[...]

> > Isn't this however checking against the current (dynamic) number of
> > runnable tasks/groups instead of the "static" group membership (which
> > shouldn't be affected by a task running state)?
> 
> Ah, you are sure. I forgot that rt_nr_running does not contain sleeping tasks.
> We need to check something else here. I'll try to find another way.

n/p. Maybe a per rt_rq flag linked to "static" membership (I didn't
really thought this through though :).

BTW, since you faced this problem, I guess this is on RT_GROUP_SCHED
enabled boxes, so I'd have a couple of questions (not strictly related
to the problem at hand):

 - do such boxes rely on RT throttling being performed at root level?
 - is RT_RUNTIME_SHARE enabled?

Thanks,

- Juri