linux-kernel - Re: [PATCH 04/19] sched/fair: Introduce a static key to enable cache aware only for multi LLCs

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Message-ID: <a5571bff-1bf8-4685-86cd-962be61427ba@intel.com>
Date: Fri, 17 Oct 2025 10:08:43 +0800
From: "Chen, Yu C" <yu.c.chen@...el.com>
To: Peter Zijlstra <peterz@...radead.org>
CC: Shrikanth Hegde <sshegde@...ux.ibm.com>, Ingo Molnar <mingo@...hat.com>,
	"K Prateek Nayak" <kprateek.nayak@....com>, "Gautham R . Shenoy"
	<gautham.shenoy@....com>, Vincent Guittot <vincent.guittot@...aro.org>, "Juri
 Lelli" <juri.lelli@...hat.com>, Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, "Mel
 Gorman" <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>, "Madadi
 Vineeth Reddy" <vineethr@...ux.ibm.com>, Hillf Danton <hdanton@...a.com>,
	Jianyong Wu <jianyong.wu@...look.com>, Yangyu Chen <cyy@...self.name>,
	Tingyin Duan <tingyin.duan@...il.com>, Vern Hao <vernhao@...cent.com>, "Len
 Brown" <len.brown@...el.com>, Aubrey Li <aubrey.li@...el.com>, Zhao Liu
	<zhao1.liu@...el.com>, Chen Yu <yu.chen.surf@...il.com>, Adam Li
	<adamli@...amperecomputing.com>, Tim Chen <tim.c.chen@...el.com>,
	<linux-kernel@...r.kernel.org>, Tim Chen <tim.c.chen@...ux.intel.com>
Subject: Re: [PATCH 04/19] sched/fair: Introduce a static key to enable cache
 aware only for multi LLCs

On 10/16/2025 3:42 PM, Peter Zijlstra wrote:
> On Thu, Oct 16, 2025 at 01:01:05AM +0800, Chen, Yu C wrote:
> 
>> Oh, do you mean only using sched_cache_allowed in sched_cache_enabled()?
>> I misunderstood that Peter suggested introducing only one key. But I didn't
>> quite catch up - do you mean we should monitor the switch of FEAT, modify
>> sched_cache_allowed when needed, and that the OS only queries
>> sched_cache_allowed
>> at runtime?
> 
> Just don't use sched_feat(), add a debugfs file like numa_balancing and
> then combine the userspace and topology information when setting the one
> static_branch.

Got it, will do like this.

thanks,
Chenyu