linux-kernel - Re: [PATCH] sched/fair: Propagate load for throttled cfs

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Message-ID: <20250910095503.GA261@bytedance>
Date: Wed, 10 Sep 2025 17:55:03 +0800
From: Aaron Lu <ziqianlu@...edance.com>
To: K Prateek Nayak <kprateek.nayak@....com>,
	Peter Zijlstra <peterz@...radead.org>
Cc: kernel test robot <lkp@...el.com>, oe-kbuild-all@...ts.linux.dev,
	Valentin Schneider <vschneid@...hat.com>,
	Ben Segall <bsegall@...gle.com>,
	Chengming Zhou <chengming.zhou@...ux.dev>,
	Josh Don <joshdon@...gle.com>, Ingo Molnar <mingo@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Xi Wang <xii@...gle.com>, linux-kernel@...r.kernel.org,
	Juri Lelli <juri.lelli@...hat.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>, Mel Gorman <mgorman@...e.de>,
	Chuyi Zhou <zhouchuyi@...edance.com>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Florian Bezdeka <florian.bezdeka@...mens.com>,
	Songtang Liu <liusongtang@...edance.com>,
	Chen Yu <yu.c.chen@...el.com>,
	Matteo Martelli <matteo.martelli@...ethink.co.uk>,
	Michal <mkoutny@...e.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH] sched/fair: Propagate load for throttled cfs_rq

On Tue, Sep 09, 2025 at 02:27:15PM +0800, Aaron Lu wrote:
> On Tue, Sep 09, 2025 at 11:52:55AM +0530, K Prateek Nayak wrote:
> > Hello Aaron,
> > 
> > On 9/9/2025 11:47 AM, Aaron Lu wrote:
> > >>>> kernel/sched/fair.c:6747:1: error: expected identifier or '(' before '+' token
> > >>     6747 | +static inline bool cfs_rq_pelt_clock_throttled(struct cfs_rq *cfs_rq)
> > >>          | ^
> > > 
> > > Sigh, I remembered I did a build test with !CFS_BANDWIDTH and now I went
> > > to check that build directory and noticed I didn't have CFS_BANDWIDTH
> > > disabled...
> > > 
> > > Sorry for the trouble, will send an updated patch later.
> > 
> > While at it, another nit.
> > 
> > On 9/8/2025 4:35 PM, Aaron Lu wrote:
> > > @@ -13151,10 +13161,13 @@ static void propagate_entity_cfs_rq(struct sched_entity *se)
> > >  {
> > >  	struct cfs_rq *cfs_rq = cfs_rq_of(se);
> > >  
> > > -	if (cfs_rq_throttled(cfs_rq))
> > > -		return;
> > > -
> > > -	if (!throttled_hierarchy(cfs_rq))
> > > +	/*
> > > +	 * If a task gets attached to this cfs_rq and before being queued,
> > > +	 * it gets migrated to another CPU due to reasons like cpuset change,
> > > +	 * we need to make sure this cfs_rq stays on leaf cfs_rq list to
> > > +	 * have that removed load decayed or it can cause faireness problem.
> > > +	 */
> > > +	if(!cfs_rq_pelt_clock_throttled(cfs_rq))
> > 
> >           ^ Can you also add a space after the "if" here.
> >
> 
> Yeah, I definitely should do that, thanks for catching this.
> 
> > >  		list_add_leaf_cfs_rq(cfs_rq);
> > 

Just a note that the updated patch is sent here:
https://lore.kernel.org/lkml/20250910095044.278-2-ziqianlu@bytedance.com/