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Date: Wed, 15 Oct 2025 17:24:02 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>,
	K Prateek Nayak <kprateek.nayak@amd.com>,
	"Gautham R . Shenoy" <gautham.shenoy@amd.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Valentin Schneider <vschneid@redhat.com>,
	Madadi Vineeth Reddy <vineethr@linux.ibm.com>,
	Hillf Danton <hdanton@sina.com>,
	Shrikanth Hegde <sshegde@linux.ibm.com>,
	Jianyong Wu <jianyong.wu@outlook.com>,
	Yangyu Chen <cyy@cyyself.name>,
	Tingyin Duan <tingyin.duan@gmail.com>,
	Vern Hao <vernhao@tencent.com>, Len Brown <len.brown@intel.com>,
	Aubrey Li <aubrey.li@intel.com>, Zhao Liu <zhao1.liu@intel.com>,
	Chen Yu <yu.chen.surf@gmail.com>, Chen Yu <yu.c.chen@intel.com>,
	Libo Chen <libo.chen@oracle.com>,
	Adam Li <adamli@os.amperecomputing.com>,
	Tim Chen <tim.c.chen@intel.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 11/19] sched/fair: Identify busiest sched_group for
 LLC-aware load balancing
Message-ID: <20251015152402.GE3168635@noisy.programming.kicks-ass.net>
References: <cover.1760206683.git.tim.c.chen@linux.intel.com>
 <fcdf37780eeb409cf10925f8b8dcef486c92b218.1760206683.git.tim.c.chen@linux.intel.com>
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In-Reply-To: <fcdf37780eeb409cf10925f8b8dcef486c92b218.1760206683.git.tim.c.chen@linux.intel.com>

On Sat, Oct 11, 2025 at 11:24:48AM -0700, Tim Chen wrote:

> @@ -11035,6 +11059,17 @@ static bool update_sd_pick_busiest(struct lb_env *env,
>  	     sds->local_stat.group_type != group_has_spare))
>  		return false;
>  
> +	/* deal with prefer LLC load balance, if failed, fall into normal load balance */
> +	if (update_llc_busiest(env, busiest, sgs))
> +		return true;
> +
> +	/*
> +	 * If the busiest group has tasks with LLC preference,
> +	 * skip normal load balance.
> +	 */
> +	if (busiest->group_llc_balance)
> +		return false;
> +
>  	if (sgs->group_type > busiest->group_type)
>  		return true;

This feels weird.. should we really override things like group_imbalance
or group_misfit_task ?