linux-kernel - Re: [PATCHv2] sched/fair: Skip SCHED_IDLE rq for SCHED

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Message-ID: <097c6b1a-6b1e-48b9-813f-31de79e883b6@amd.com>
Date: Wed, 4 Feb 2026 13:24:58 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Shubhang Kaushik <shubhang@...amperecomputing.com>, Christian Loehle
	<christian.loehle@....com>, <linux-kernel@...r.kernel.org>,
	<peterz@...radead.org>, <mingo@...hat.com>, <vincent.guittot@...aro.org>
CC: <juri.lelli@...hat.com>, <dietmar.eggemann@....com>,
	<pierre.gondois@....com>
Subject: Re: [PATCHv2] sched/fair: Skip SCHED_IDLE rq for SCHED_IDLE task

Hello Shubhang,

On 2/4/2026 7:38 AM, Shubhang Kaushik wrote:
>> @@ -12299,7 +12305,7 @@ static void sched_balance_domains(struct rq *rq, enum cpu_idle_type idle)
>>                  * state even if we migrated tasks. Update it.
>>                  */
>>                 idle = idle_cpu(cpu);
>> -                busy = !idle && !sched_idle_cpu(cpu);
>> +                busy = !idle && !sched_idle_rq(rq);
> 
> Usually sched_idle_rqs were treated as not-busy in several balancing decisions to avoid yielding to background load. Does this change alter that interpretation at the domain balancing level ?

I don't think anything changes in the load-balancer path since we still
check for sched_idle_rq() here. Only the wakeup path will consider both
the waking task's policy and whether the CPU is completely idle vs
sched_idle_rq().

> 
>>             }
>>             sd->last_balance = jiffies;
>>             interval = get_sd_balance_interval(sd, busy);
-- 
Thanks and Regards,
Prateek