linux-kernel - Re: [PATCH v2 16/23] sched/cache: Introduce sched_cache_present to enable cache aware scheduling for multi LLCs NUMA node

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251210165257.GB3708021@noisy.programming.kicks-ass.net>
Date: Wed, 10 Dec 2025 17:52:57 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Tim Chen <tim.c.chen@...ux.intel.com>
Cc: Ingo Molnar <mingo@...hat.com>,
	K Prateek Nayak <kprateek.nayak@....com>,
	"Gautham R . Shenoy" <gautham.shenoy@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Chen Yu <yu.c.chen@...el.com>, 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>,
	Shrikanth Hegde <sshegde@...ux.ibm.com>,
	Jianyong Wu <jianyong.wu@...look.com>,
	Yangyu Chen <cyy@...self.name>,
	Tingyin Duan <tingyin.duan@...il.com>,
	Vern Hao <vernhao@...cent.com>, Vern Hao <haoxing990@...il.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>,
	Aaron Lu <ziqianlu@...edance.com>, Tim Chen <tim.c.chen@...el.com>,
	linux-kernel@...r.kernel.org, Libo Chen <libo.chen@...cle.com>
Subject: Re: [PATCH v2 16/23] sched/cache: Introduce sched_cache_present to
 enable cache aware scheduling for multi LLCs NUMA node

On Wed, Dec 10, 2025 at 05:32:35PM +0100, Peter Zijlstra wrote:
> On Wed, Dec 03, 2025 at 03:07:35PM -0800, Tim Chen wrote:
> > From: Chen Yu <yu.c.chen@...el.com>
> > 
> > Cache-aware load balancing should only be enabled if there are more
> > than 1 LLCs within 1 NUMA node. sched_cache_present is introduced to
> > indicate whether this platform supports this topology.
> > 
> > Suggested-by: Libo Chen <libo.chen@...cle.com>
> > Suggested-by: Adam Li <adamli@...amperecomputing.com>
> > Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> > Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
> > ---
> > 
> > Notes:
> >     v1->v2:
> >     	Use flag sched_cache_present to indicate whether a platform
> >     	supports cache aware scheduling. Change this flag from staic key.
> >     	There should be only 1 static key to control the cache aware
> >     	scheduling. (Peter Zijlstra)
> > 
> >  kernel/sched/topology.c | 20 +++++++++++++++-----
> >  1 file changed, 15 insertions(+), 5 deletions(-)
> > 
> > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> > index d583399fc6a1..9799e3a9a609 100644
> > --- a/kernel/sched/topology.c
> > +++ b/kernel/sched/topology.c
> > @@ -24,6 +24,8 @@ int max_llcs;
> >  
> >  #ifdef CONFIG_SCHED_CACHE
> >  
> > +static bool sched_cache_present;
> 
> sched_energy_present
> sched_asym_cpucapacity
> sched_cluster_active
> sched_smt_present
> 
> are all static keys tied to the current topology, why break the streak
> and make this a boolean?

Also, patch doesn't use sched_cache_present at all, so perhaps just drop
it on the floor entirely?