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From: Mel Gorman <mgorman@techsingularity.net>
To: Hillf Danton <hdanton@sina.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
	Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Phil Auld <pauld@redhat.com>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 08/11] sched/numa: Bias swapping tasks based on their preferred node
Date: Fri, 14 Feb 2020 07:50:45 +0000	[thread overview]
Message-ID: <20200214075045.GB3466@techsingularity.net> (raw)
In-Reply-To: <20200214041232.18904-1-hdanton@sina.com>

On Fri, Feb 14, 2020 at 12:12:32PM +0800, Hillf Danton wrote:
> > +	if (cur->numa_preferred_nid == env->dst_nid)
> > +		imp -= imp / 16;
> > +
> > +	/*
> > +	 * Encourage picking a task that moves to its preferred node.
> > +	 * This potentially makes imp larger than it's maximum of
> > +	 * 1998 (see SMALLIMP and task_weight for why) but in this
> > +	 * case, it does not matter.
> > +	 */
> > +	if (cur->numa_preferred_nid == env->src_nid)
> > +		imp += imp / 8;
> > +
> >  	if (maymove && moveimp > imp && moveimp > env->best_imp) {
> >  		imp = moveimp;
> >  		cur = NULL;
> >  		goto assign;
> >  	}
> >  
> > +	/*
> > +	 * If a swap is required then prefer moving a task to its preferred
> > +	 * nid over a task that is not moving to a preferred nid.
> 
> after checking if imp is above SMALLIMP.
> 

It is preferable to move a task to its preferred node over one that
does not even if the improvement is lsss than SMALLIMP. The reasoning is
that NUMA balancing retries moving tasks to their preferred node
periodically and moving "now" reduces the chance of a task having to
retry its move later.

-- 
Mel Gorman
SUSE Labs

      parent reply	other threads:[~2020-02-14  7:50 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-12  9:36 [RFC PATCH 00/11] Reconcile NUMA balancing decisions with the load balancer Mel Gorman
2020-02-12  9:36 ` [PATCH 01/11] sched/fair: Allow a small load imbalance between low utilisation SD_NUMA domains Mel Gorman
2020-02-12  9:36 ` [PATCH 02/11] sched/fair: Optimize select_idle_core() Mel Gorman
2020-02-12  9:36 ` [PATCH 03/11] sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression Mel Gorman
2020-02-12  9:36 ` [PATCH 04/11] sched/numa: Trace when no candidate CPU was found on the preferred node Mel Gorman
2020-02-12  9:36 ` [PATCH 05/11] sched/numa: Distinguish between the different task_numa_migrate failure cases Mel Gorman
2020-02-12 14:43   ` Steven Rostedt
2020-02-12 15:59     ` Mel Gorman
2020-02-12  9:36 ` [PATCH 06/11] sched/numa: Prefer using an idle cpu as a migration target instead of comparing tasks Mel Gorman
2020-02-12  9:36 ` [PATCH 07/11] sched/numa: Find an alternative idle CPU if the CPU is part of an active NUMA balance Mel Gorman
2020-02-12  9:36 ` [PATCH 08/11] sched/numa: Bias swapping tasks based on their preferred node Mel Gorman
2020-02-13 10:31   ` Peter Zijlstra
2020-02-13 11:18     ` Mel Gorman
2020-02-12 13:22 ` [RFC PATCH 00/11] Reconcile NUMA balancing decisions with the load balancer Vincent Guittot
2020-02-12 14:07   ` Valentin Schneider
2020-02-12 15:48   ` Mel Gorman
2020-02-12 16:13     ` Vincent Guittot
2020-02-12 15:45 ` [PATCH 09/11] sched/fair: Split out helper to adjust imbalances between domains Mel Gorman
2020-02-12 15:46 ` [PATCH 10/11] sched/numa: Use similar logic to the load balancer for moving between domains with spare capacity Mel Gorman
2020-02-12 15:46 ` [PATCH 11/11] sched/numa: Use similar logic to the load balancer for moving between overloaded domains Mel Gorman
     [not found] ` <20200214041232.18904-1-hdanton@sina.com>
2020-02-14  7:50   ` Mel Gorman [this message]

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