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

[Chen, Yu C]

On 12/11/2025 12:52 AM, Peter Zijlstra wrote:
> 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@xxxxxxxxx>
> > >
> > > 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@xxxxxxxxxx>
> > > Suggested-by: Adam Li <adamli@xxxxxxxxxxxxxxxxxxxxxx>
> > > Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
> > > Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> > > ---
> > >
> > > 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?

The sched_cache_present flag is used in a subsequent patch:
"[20/23] sched/cache: Add user control to adjust the parameters of 
cache-aware
scheduling" This flag is used to check whether the user is eligible to 
enable
cache-aware scheduling. I will try to place the declaration and usage of 
this
flag together.

thanks,
Chenyu