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Date: Wed, 15 Oct 2025 14:05:23 +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 07/19] sched/fair: Track LLC-preferred tasks per runqueue
Message-ID: <20251015120523.GT3289052@noisy.programming.kicks-ass.net>
References: <cover.1760206683.git.tim.c.chen@linux.intel.com>
 <ccbfda37200b66177a1c1add4715a49b863ac84d.1760206683.git.tim.c.chen@linux.intel.com>
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In-Reply-To: <ccbfda37200b66177a1c1add4715a49b863ac84d.1760206683.git.tim.c.chen@linux.intel.com>

On Sat, Oct 11, 2025 at 11:24:44AM -0700, Tim Chen wrote:
> @@ -3999,6 +4038,7 @@ account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
>  		struct rq *rq = rq_of(cfs_rq);
>  
>  		account_numa_enqueue(rq, task_of(se));
> +		account_llc_enqueue(rq, task_of(se));
>  		list_add(&se->group_node, &rq->cfs_tasks);

Here and...

>  	}
>  	cfs_rq->nr_queued++;
> @@ -4010,9 +4050,14 @@ account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
>  	update_load_sub(&cfs_rq->load, se->load.weight);
>  	if (entity_is_task(se)) {
>  		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
> +		account_llc_dequeue(rq_of(cfs_rq), task_of(se));

... here, could you please check the compiler is doing CSE of task_of()?

>  		list_del_init(&se->group_node);
>  	}
>  	cfs_rq->nr_queued--;
> +
> +	/* safeguard to clear the cache aware data */
> +	if (!parent_entity(se) && !cfs_rq->nr_queued)
> +		reset_llc_stats(rq_of(cfs_rq));

I'm confused -- why?