Re: [PATCH v2 5/5] mm: Add update_mmu_tlb_range()

[Bang Li]

Hey Lance,

Thanks for taking time to review!

On 2024/5/7 0:07, Lance Yang wrote:
> On Mon, May 6, 2024 at 11:52 PM Bang Li <libang.li@xxxxxxxxxxxx> wrote:
> > After the commit 19eaf44954df ("mm: thp: support allocation of anonymous
> > multi-size THP"), it may need to batch update tlb of an address range
> > through the update_mmu_tlb function. We can simplify this operation by
> > adding the update_mmu_tlb_range function, which may also reduce the
> > execution of some unnecessary code in some architectures.
> >
> > Signed-off-by: Bang Li <libang.li@xxxxxxxxxxxx>
> > ---
> >   include/linux/pgtable.h | 8 ++++++++
> >   mm/memory.c             | 4 +---
> >   2 files changed, 9 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> > index 18019f037bae..869bfe6054f1 100644
> > --- a/include/linux/pgtable.h
> > +++ b/include/linux/pgtable.h
> > @@ -737,6 +737,14 @@ static inline void update_mmu_tlb(struct vm_area_struct *vma,
> >   #define __HAVE_ARCH_UPDATE_MMU_TLB
> >   #endif
> >
> > +#ifndef __HAVE_ARCH_UPDATE_MMU_TLB_RANGE
>
> IIRC, the contemporary practice is to define a macro with the same name
> as the function if it is being overridden.

The macro __HAVE_ARCH_UPDATE_MMU_TLB_RANGE defined here is aligned with
the macro __HAVE_ARCH_UPDATE_MMU_TLB corresponding to the update_mmu_tlb
function. IMO, it should be better to use my method in this case.

Thanks,
Bang

> Thanks,
> Lance
>
> > +static inline void update_mmu_tlb_range(struct vm_area_struct *vma,
> > +                               unsigned long address, pte_t *ptep, unsigned int nr)
> > +{
> > +}
> > +#define __HAVE_ARCH_UPDATE_MMU_TLB_RANGE
> > +#endif
> > +
> >   /*
> >    * Some architectures may be able to avoid expensive synchronization
> >    * primitives when modifications are made to PTE's which are already
> > diff --git a/mm/memory.c b/mm/memory.c
> > index eea6e4984eae..2d53e29cf76e 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -4421,7 +4421,6 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
> >          vm_fault_t ret = 0;
> >          int nr_pages = 1;
> >          pte_t entry;
> > -       int i;
> >
> >          /* File mapping without ->vm_ops ? */
> >          if (vma->vm_flags & VM_SHARED)
> > @@ -4491,8 +4490,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
> >                  update_mmu_tlb(vma, addr, vmf->pte);
> >                  goto release;
> >          } else if (nr_pages > 1 && !pte_range_none(vmf->pte, nr_pages)) {
> > -               for (i = 0; i < nr_pages; i++)
> > -                       update_mmu_tlb(vma, addr + PAGE_SIZE * i, vmf->pte + i);
> > +               update_mmu_tlb_range(vma, addr, vmf->pte, nr_pages);
> >                  goto release;
> >          }
> >
> > --
> > 2.19.1.6.gb485710b