linux-kernel - Re: [PATCH v2 00/12] sched: Address schbench regression

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Message-ID: <21eb2e07-7ac9-42ef-a8f7-15a01a3c1629@meta.com>
Date: Tue, 8 Jul 2025 11:09:06 -0400
From: Chris Mason <clm@...a.com>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org, mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        vschneid@...hat.com
Subject: Re: [PATCH v2 00/12] sched: Address schbench regression

On 7/7/25 5:05 AM, Shrikanth Hegde wrote:
> 
> 
> On 7/2/25 17:19, Peter Zijlstra wrote:
>> Hi!
>>
>> Previous version:
>>
>>    https://lkml.kernel.org/r/20250520094538.086709102@infradead.org
>>
>> Changes:
>>   - keep dl_server_stop(), just remove the 'normal' usage of it (juril)
>>   - have the sched_delayed wake list IPIs do select_task_rq() (vingu)
>>   - fixed lockdep splat (dietmar)
>>   - added a few preperatory patches
>>
>>
>> Patches apply on top of tip/master (which includes the disabling of
>> private futex)
>> and clm's newidle balance patch (which I'm awaiting vingu's ack on).
>>
>> Performance is similar to the last version; as tested on my SPR on
>> v6.15 base:
>>
> 
> 
> Hi Peter,
> Gave this a spin on a machine with 5 cores (SMT8) PowerPC system.
> 
> I see significant regression in schbench. let me know if i have to test
> different
> number of threads based on the system size.
> Will go through the series and will try a bisect meanwhile.

Not questioning the git bisect results you had later in this thread, but
double checking that you had the newidle balance patch in place that
Peter mentioned?

https://lore.kernel.org/lkml/20250626144017.1510594-2-clm@fb.com/

The newidle balance frequency changes the cost of everything else, so I
wanted to make sure we were measuring the same things.

Thanks!

-chris