Re: [RFC PATCH v3 1/3] mm: Factor out the pagetable pages account into new helper function

[Baolin Wang]

On 6/30/2022 10:11 PM, Mike Rapoport wrote:
> On Thu, Jun 30, 2022 at 07:11:14PM +0800, Baolin Wang wrote:
> > Factor out the pagetable pages account into new helper functions to avoid
> > duplicated code. Meanwhile these helper functions also will be used to
> > account pagetable pages which do not need split pagetale lock.
> >
> > Meanwhile convert to use mod_lruvec_page_state() in case of non-order-0
> > page table allocation.
>
> These are *very* rare. I think only parisc may have non-order-0 pmd and pud
> tables.

s390 also has non-order-0 page table allocation, but they both do not 
use the generic page table allocation now.

> With that, I'd suggest making use of compound_nr() build time opt-in.

After more thinking, I'd prefer to change back to use 
inc_lruvec_page_state()/dec_lruvec_page_state(), since now no 
architecures will need non-order-0 page table allocation.

After this patchset, I plan to convert parisc and s390 to use generic 
pagetable allocation, then I will add non-order-0 page table allocation 
support. Like Matthew suggested, maybe I need change the API to pass the 
number of pages.

> > Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> > ---
> >   include/linux/mm.h | 24 ++++++++++++++++--------
> >   1 file changed, 16 insertions(+), 8 deletions(-)
> >
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index a2270e3..3be6d2c 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -2353,20 +2353,30 @@ static inline void pgtable_init(void)
> >   	pgtable_cache_init();
> >   }
> >   
> > +static inline void pgtable_page_inc(struct page *page)
> > +{
> > +	__SetPageTable(page);
> > +	mod_lruvec_page_state(page, NR_PAGETABLE, compound_nr(page));
> > +}
> > +
> > +static inline void pgtable_page_dec(struct page *page)
> > +{
> > +	__ClearPageTable(page);
> > +	mod_lruvec_page_state(page, NR_PAGETABLE, -compound_nr(page));
> > +}
> > +
> >   static inline bool pgtable_pte_page_ctor(struct page *page)
> >   {
> >   	if (!ptlock_init(page))
> >   		return false;
> > -	__SetPageTable(page);
> > -	inc_lruvec_page_state(page, NR_PAGETABLE);
> > +	pgtable_page_inc(page);
> >   	return true;
> >   }
> >   
> >   static inline void pgtable_pte_page_dtor(struct page *page)
> >   {
> >   	ptlock_free(page);
> > -	__ClearPageTable(page);
> > -	dec_lruvec_page_state(page, NR_PAGETABLE);
> > +	pgtable_page_dec(page);
> >   }
> >   
> >   #define pte_offset_map_lock(mm, pmd, address, ptlp)	\
> > @@ -2452,16 +2462,14 @@ static inline bool pgtable_pmd_page_ctor(struct page *page)
> >   {
> >   	if (!pmd_ptlock_init(page))
> >   		return false;
> > -	__SetPageTable(page);
> > -	inc_lruvec_page_state(page, NR_PAGETABLE);
> > +	pgtable_page_inc(page);
> >   	return true;
> >   }
> >   
> >   static inline void pgtable_pmd_page_dtor(struct page *page)
> >   {
> >   	pmd_ptlock_free(page);
> > -	__ClearPageTable(page);
> > -	dec_lruvec_page_state(page, NR_PAGETABLE);
> > +	pgtable_page_dec(page);
> >   }
> >   
> >   /*
> > --
> > 1.8.3.1