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From: Mel Gorman <mgorman@techsingularity.net>
To: "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Aubrey Li <aubrey.li@linux.intel.com>,
	yangyicong <yangyicong@huawei.com>
Subject: Re: [PATCH 7/9] sched/fair: Enforce proportional scan limits when scanning for an idle core
Date: Wed, 4 Aug 2021 11:22:36 +0100	[thread overview]
Message-ID: <20210804102236.GB6464@techsingularity.net> (raw)
In-Reply-To: <58167022b9074ed9951b09ab6ba1983e@hisilicon.com>

On Mon, Aug 02, 2021 at 10:52:01AM +0000, Song Bao Hua (Barry Song) wrote:
> > @@ -6265,30 +6265,35 @@ static int select_idle_cpu(struct task_struct *p, struct
> > sched_domain *sd, bool
> >  		if (has_idle_core) {
> >  			i = select_idle_core(p, cpu, cpus, &idle_cpu);
> >  			if ((unsigned int)i < nr_cpumask_bits)
> > -				return i;
> > +				break;
> > 
> > +			nr -= sched_smt_weight;
> >  		} else {
> > -			if (!--nr)
> > -				return -1;
> >  			idle_cpu = __select_idle_cpu(cpu, p);
> >  			if ((unsigned int)idle_cpu < nr_cpumask_bits)
> >  				break;
> > +			nr--;
> >  		}
> > +
> > +		if (nr < 0)
> > +			break;
> >  	}
> > 
> > -	if (has_idle_core)
> > -		set_idle_cores(target, false);
> > +	if ((unsigned int)idle_cpu < nr_cpumask_bits) {
> > +		if (has_idle_core)
> > +			set_idle_cores(target, false);
> > 
> 
> For example, if we have 16 cpus(8 SMT2 cores). In case core7 is idle,
> we only have scanned core0+core1(cpu0-cpu3) and if these two cores
> are not idle, but here we set has_idle_cores to false while core7 is
> idle. It seems incorrect.
> 

Yep, that block needs to be revisited.

-- 
Mel Gorman
SUSE Labs

  reply	other threads:[~2021-08-04 10:22 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-26 10:22 [RFC PATCH 0/9] Modify and/or delete SIS_PROP Mel Gorman
2021-07-26 10:22 ` [PATCH 1/9] sched/fair: Track efficiency of select_idle_sibling Mel Gorman
2021-07-26 10:22 ` [PATCH 2/9] sched/fair: Track efficiency of task recent_used_cpu Mel Gorman
2021-07-26 10:22 ` [PATCH 3/9] sched/fair: Track efficiency of select_idle_core Mel Gorman
2021-07-26 10:22 ` [PATCH 4/9] sched/fair: Use prev instead of new target as recent_used_cpu Mel Gorman
2021-07-26 10:22 ` [PATCH 5/9] sched/fair: Avoid a second scan of target in select_idle_cpu Mel Gorman
2021-07-26 10:22 ` [PATCH 6/9] sched/fair: Make select_idle_cpu() proportional to cores Mel Gorman
2021-07-26 10:22 ` [PATCH 7/9] sched/fair: Enforce proportional scan limits when scanning for an idle core Mel Gorman
2021-08-02 10:52   ` Song Bao Hua (Barry Song)
2021-08-04 10:22     ` Mel Gorman [this message]
2021-07-26 10:22 ` [PATCH 8/9] sched/fair: select idle cpu from idle cpumask for task wakeup Mel Gorman
2021-08-02 10:41   ` Song Bao Hua (Barry Song)
2021-08-04 10:26     ` Mel Gorman
2021-08-05  0:23       ` Aubrey Li
2021-09-17  3:44         ` Barry Song
2021-09-17  4:15         ` Barry Song
2021-09-17  9:11           ` Aubrey Li
2021-09-17 13:35             ` Mel Gorman
2021-07-26 10:22 ` [PATCH 9/9] sched/core: Delete SIS_PROP and rely on the idle cpu mask Mel Gorman

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