linux-kernel - Re: [External] : Re: [REGRESSION][v6.17-rc1]sched/fair: Bump sd->max_newidle_lb

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Message-ID: <5e236e56-5fbb-48a3-84a7-839f4ab08f6d@oracle.com>
Date: Fri, 31 Oct 2025 17:16:30 -0400
From: Joseph Salisbury <joseph.salisbury@...cle.com>
To: Adam Li <adamli@...amperecomputing.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc: Chris Mason <clm@...a.com>, clm@...com,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>, Ingo Molnar <mingo@...hat.com>,
        dietmar.eggemann@....com, Steven Rostedt <rostedt@...dmis.org>,
        bsegall@...gle.com, mgorman@...e.de, vschneid@...hat.com,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [External] : Re: [REGRESSION][v6.17-rc1]sched/fair: Bump
 sd->max_newidle_lb_cost when newidle balance fails



On 10/30/25 3:29 AM, Adam Li wrote:
> Hi Joseph,
>
> On 10/18/2025 1:01 AM, Joseph Salisbury wrote:
>>
>> On 10/10/25 13:09, Peter Zijlstra wrote:
>>> On Thu, Oct 09, 2025 at 09:04:40PM -0400, Joseph Salisbury wrote:
>>>
> [...]
>>> diff --git a/kernel/sched/features.h b/kernel/sched/features.h
>>> index 3c12d9f93331..5ded210701d0 100644
>>> --- a/kernel/sched/features.h
>>> +++ b/kernel/sched/features.h
>>> @@ -121,3 +121,8 @@ SCHED_FEAT(WA_BIAS, true)
>>>    SCHED_FEAT(UTIL_EST, true)
>>>      SCHED_FEAT(LATENCY_WARN, false)
>>> +
>>> +SCHED_FEAT(NI_TARGET, false)
>>> +SCHED_FEAT(NI_SPARE, false)
>>> +SCHED_FEAT(NI_RUNNABLE, false)
>>> +SCHED_FEAT(NI_RANDOM, false)
> [...]
>> Thanks for providing the patch!
>>
>> I performed the same testing with this patch applied to a v6.12 based kernel.  The performance regression still exists and is slightly worse.
>> The drgn stats are attached in a file named 'apache_drgn_log_NewidleRework_From_Peter.log'.
>>
>>
> Just wondering, did you enable NI_TARGET feature?
> It is default false in Peter's patch.
> In my test 'NI_TARGET' can fix the regression caused by commit 155213a2aed4.
>
> Thanks,
> -adam
>
Hi Adam,

I did not try NI_TARGET.  I will try changing this in Peter's patch and 
re-test.  I'll post the results.