Re: [PATCH v2 1/4] mm: support promotion-only NUMA hinting scans

[Gregory Price <gourry@gourry.net>]

On Thu, Sep 17, 2026 at 06:03:28PM +0200, Peter Zijlstra wrote:
> On Thu, Sep 10, 2026 at 08:18:23PM -0400, Gregory Price wrote:
> 
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 8dff37059faf..81359b414947 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -4129,8 +4129,10 @@ static void task_numa_work(struct callback_head *work)
> >  	unsigned long nr_pte_updates = 0;
> >  	long pages, virtpages;
> >  	struct vma_iterator vmi;
> > +	unsigned int numab_mode = READ_ONCE(sysctl_numa_balancing_mode);
> 
> This thing sticks out like a sort thumb, does that want to be on top?
> Typically reverse xmas is preferred and all that.
> 

oi yeah sorry, should have given this a closer style look.

will fix it up.

> >  	bool vma_pids_skipped;
> >  	bool vma_pids_forced = false;
> > +	bool promo_only;
> >  
> >  	WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
> >  
> 
> > --- a/mm/internal.h
> > +++ b/mm/internal.h
> > @@ -1237,11 +1237,12 @@ static inline bool vma_is_single_threaded_private(struct vm_area_struct *vma)
> >  
> >  #ifdef CONFIG_NUMA_BALANCING
> >  bool folio_can_map_prot_numa(struct folio *folio, struct vm_area_struct *vma,
> > -		bool is_private_single_threaded);
> > +		bool is_private_single_threaded, bool promo_only);
> 
> Two bools rather than updating the existing bool to a flags?

every time i've added a flag field someone screeches at me, so I tend
to avoid it now - but i can do that's the preference here.

Otherwise, i tend to follow rule of 3 for generalizing.

~Gregory