linux-kernel - Re: [PATCH v1] sched/uclamp: Exclude kernel threads from uclamp logic

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Message-ID: <36dec74c-67eb-44f2-8709-d0eb9c65987a@kylinos.cn>
Date: Tue, 15 Jul 2025 13:59:06 +0800
From: Zihuan Zhang <zhangzihuan@...inos.cn>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Christian Loehle <christian.loehle@....com>, xuewen.yan@...soc.com,
 vincent.guittot@...aro.org, mingo@...hat.com, peterz@...radead.org,
 juri.lelli@...hat.com, bsegall@...gle.com, mgorman@...e.de,
 vschneid@...hat.com, hongyan.xia2@....com, linux-kernel@...r.kernel.org,
 ke.wang@...soc.com, di.shen@...soc.com, xuewen.yan94@...il.com,
 kprateek.nayak@....com, kuyo.chang@...iatek.com, juju.sung@...iatek.com,
 qyousef@...alina.io
Subject: Re: [PATCH v1] sched/uclamp: Exclude kernel threads from uclamp logic


在 2025/7/10 22:03, Steven Rostedt 写道:
> On Thu, 10 Jul 2025 08:55:28 +0800
> Zihuan Zhang <zhangzihuan@...inos.cn> wrote:
>
>> The motivation behind this patch is to explore whether it’s worth
>> optimizing the uclamp hot path a bit further. Since kernel threads
>> typically don’t benefit from uclamp adjustments and often just inherit
>> default values (e.g., max=1024), we were wondering if skipping the
>> aggregation logic for such cases could slightly reduce overhead in some
>> workloads.
>>
>> Of course, we want to be conservative and avoid breaking any legitimate
>> usage. So I’d love to hear your opinion — do you think it’s worthwhile
>> to pursue this kind of micro-optimization in uclamp, or is the potential
>> gain too marginal to justify the added logic?
> My honest opinion is that if there's not a huge issue you are trying
> to solve, then it's best to leave things as is. Tweaking this for
> micro-optimizations usually end up causing a regression somewhere you
> never expected.
>
> -- Steve
Thanks for the advice! I’ll keep that in mind for my next patch.

Best regards,
Zihuan Zhang