Re: [PATCH 07/34] sched_ext: Introduce cgroup sub-sched support

[Tejun Heo]

Hello,

On Thu, Feb 26, 2026 at 04:37:55PM +0100, Andrea Righi wrote:
> On Tue, Feb 24, 2026 at 07:00:42PM -1000, Tejun Heo wrote:
> ...
> > diff --git a/init/Kconfig b/init/Kconfig
> > index c25869cf59c1..96ba2fa08883 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -1176,6 +1176,10 @@ config EXT_GROUP_SCHED
> >  
> >  endif #CGROUP_SCHED
> >  
> > +config EXT_SUB_SCHED
> > +        def_bool y
> > +        depends on SCHED_CLASS_EXT
> > +
> 
> It would be nice if we could opt to not build this. Also, if I disable
> CONFIG_CGROUP:
> 
> kernel/sched/ext.c: In function ‘scx_dispatch_sched’:
> kernel/sched/ext.c:2454:52: error: ‘struct sched_ext_entity’ has no member named ‘sched’
>  2454 |                 sch == rcu_access_pointer(prev->scx.sched);
>       |                                                    ^

Build bug is fixed. We can make CONFIG_EXT_SUB_SCHED a selectable config
option, but I'm not sure what that buys us. In terms of kernel image
overhead, it's not going to be anything substantial and it shouldn't add
noticeable hot path overhead either. In general, I'm not a big fan of
introducing selectable config options unless there are justifiable benefits.

Thanks.

-- 
tejun