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From: Xuewen Yan <xuewen.yan94@gmail.com>
Date: Mon, 22 Apr 2024 19:07:25 +0800
Message-ID: <CAB8ipk9M1wLXV7MWMBYGMhKbY71QqwkvchiENeWTg7JERe6kZw@mail.gmail.com>
Subject: Re: [PATCH v2] sched/eevdf: Prevent vlag from going out of bounds
 when reweight_eevdf
To: Peter Zijlstra <peterz@infradead.org>
Cc: Xuewen Yan <xuewen.yan@unisoc.com>, mingo@redhat.com, juri.lelli@redhat.com, 
	vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, 
	bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, 
	yu.c.chen@intel.com, ke.wang@unisoc.com, di.shen@unisoc.com, 
	linux-kernel@vger.kernel.org
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On Mon, Apr 22, 2024 at 5:42=E2=80=AFPM Peter Zijlstra <peterz@infradead.or=
g> wrote:
>
> On Mon, Apr 22, 2024 at 04:33:37PM +0800, Xuewen Yan wrote:
>
> > On the Android system, the nice value of a task will change very
> > frequently. The limit can also be exceeded.
> > Maybe the !on_rq case is still necessary.
> > So I'm planning to propose another patch for !on_rq case later after
> > careful testing locally.
>
> So the scaling is: vlag =3D vlag * old_Weight / weight
>
> But given that integer devision is truncating, you could expect repeated
> application of such scaling would eventually decrease the vlag instead
> of grow it.
>
> Is there perhaps an invocation of reweight_task() missing? Looking at

Is it necessary to add reweight_task in the prio_changed_fair()?

> set_load_weight() I'm suspicious of the task_has_idle_policy() case.