Re: [v4 PATCH 4/7] mm: thp: kill transparent_hugepage_active()

[Yang Shi <shy828301@gmail.com>]

On Wed, Jun 15, 2022 at 5:17 PM Zach O'Keefe <zokeefe@google.com> wrote:
>
> On 15 Jun 10:29, Yang Shi wrote:
> > The transparent_hugepage_active() was introduced to show THP eligibility
> > bit in smaps in proc, smaps is the only user.  But it actually does the
> > similar check as hugepage_vma_check() which is used by khugepaged.  We
> > definitely don't have to maintain two similar checks, so kill
> > transparent_hugepage_active().
> >
> > This patch also fixed the wrong behavior for VM_NO_KHUGEPAGED vmas.
> >
> > Also move hugepage_vma_check() to huge_memory.c and huge_mm.h since it
> > is not only for khugepaged anymore.
> >
> > Signed-off-by: Yang Shi <shy828301@gmail.com>
> > ---
> >  fs/proc/task_mmu.c         |  2 +-
> >  include/linux/huge_mm.h    | 11 ++++++++-
> >  include/linux/khugepaged.h |  2 --
> >  mm/huge_memory.c           | 50 +++++++++++++++++++++++++++++++-------
> >  mm/khugepaged.c            | 48 +++---------------------------------
> >  5 files changed, 56 insertions(+), 57 deletions(-)
> >
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index 37ccb5c9f4f8..39a40ec181e7 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -863,7 +863,7 @@ static int show_smap(struct seq_file *m, void *v)
> >       __show_smap(m, &mss, false);
> >
> >       seq_printf(m, "THPeligible:    %d\n",
> > -                transparent_hugepage_active(vma));
> > +                hugepage_vma_check(vma, vma->vm_flags, true));
> >
> >       if (arch_pkeys_enabled())
> >               seq_printf(m, "ProtectionKey:  %8u\n", vma_pkey(vma));
> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > index 8a5a8bfce0f5..aeb13119ee28 100644
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -202,7 +202,9 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma)
> >              !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode);
> >  }
> >
> > -bool transparent_hugepage_active(struct vm_area_struct *vma);
>
> Like v3, I think this also needs to be deleted from !CONFIG_TRANSPARENT_HUGEPAGE

Oops, thanks for catching this. Will fix it.

>
> Otherwise can add
>
> Reviewed-by: Zach O'Keefe <zokeefe@google.com>
>
> > +bool hugepage_vma_check(struct vm_area_struct *vma,
> > +                     unsigned long vm_flags,
> > +                     bool smaps);
> >
> >  #define transparent_hugepage_use_zero_page()                         \
> >       (transparent_hugepage_flags &                                   \
> > @@ -368,6 +370,13 @@ static inline bool transhuge_vma_enabled(struct vm_area_struct *vma,
> >       return false;
> >  }
> >
> > +static inline bool hugepage_vma_check(struct vm_area_struct *vma,
> > +                                    unsigned long vm_flags,
> > +                                    bool smaps)
> > +{
> > +     return false;
> > +}
> > +
> >  static inline void prep_transhuge_page(struct page *page) {}
> >
> >  #define transparent_hugepage_flags 0UL
> > diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
> > index 31ca8a7f78f4..ea5fd4c398f7 100644
> > --- a/include/linux/khugepaged.h
> > +++ b/include/linux/khugepaged.h
> > @@ -10,8 +10,6 @@ extern struct attribute_group khugepaged_attr_group;
> >  extern int khugepaged_init(void);
> >  extern void khugepaged_destroy(void);
> >  extern int start_stop_khugepaged(void);
> > -extern bool hugepage_vma_check(struct vm_area_struct *vma,
> > -                            unsigned long vm_flags);
> >  extern void __khugepaged_enter(struct mm_struct *mm);
> >  extern void __khugepaged_exit(struct mm_struct *mm);
> >  extern void khugepaged_enter_vma(struct vm_area_struct *vma,
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index b530462c4493..a28c6100b491 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -69,21 +69,53 @@ static atomic_t huge_zero_refcount;
> >  struct page *huge_zero_page __read_mostly;
> >  unsigned long huge_zero_pfn __read_mostly = ~0UL;
> >
> > -bool transparent_hugepage_active(struct vm_area_struct *vma)
> > +bool hugepage_vma_check(struct vm_area_struct *vma,
> > +                     unsigned long vm_flags,
> > +                     bool smaps)
> >  {
> > -     /* The addr is used to check if the vma size fits */
> > -     unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE;
> > +     if (!transhuge_vma_enabled(vma, vm_flags))
> > +             return false;
> > +
> > +     if (vm_flags & VM_NO_KHUGEPAGED)
> > +             return false;
> > +
> > +     /* Don't run khugepaged against DAX vma */
> > +     if (vma_is_dax(vma))
> > +             return false;
> >
> > -     if (!transhuge_vma_suitable(vma, addr))
> > +     /* Check alignment for file vma and size for both file and anon vma */
> > +     if (!transhuge_vma_suitable(vma, (vma->vm_end - HPAGE_PMD_SIZE)))
> >               return false;
> > -     if (vma_is_anonymous(vma))
> > -             return __transparent_hugepage_enabled(vma);
> > -     if (vma_is_shmem(vma))
> > +
> > +     /* Enabled via shmem mount options or sysfs settings. */
> > +     if (shmem_file(vma->vm_file))
> >               return shmem_huge_enabled(vma);
> > -     if (transhuge_vma_enabled(vma, vma->vm_flags) && file_thp_enabled(vma))
> > +
> > +     if (!khugepaged_enabled())
> > +             return false;
> > +
> > +     /* THP settings require madvise. */
> > +     if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always())
> > +             return false;
> > +
> > +     /* Only regular file is valid */
> > +     if (file_thp_enabled(vma))
> >               return true;
> >
> > -     return false;
> > +     if (!vma_is_anonymous(vma))
> > +             return false;
> > +
> > +     if (vma_is_temporary_stack(vma))
> > +             return false;
> > +
> > +     /*
> > +      * THPeligible bit of smaps should show 1 for proper VMAs even
> > +      * though anon_vma is not initialized yet.
> > +      */
> > +     if (!vma->anon_vma)
> > +             return smaps;
> > +
> > +     return true;
> >  }
> >
> >  static bool get_huge_zero_page(void)
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 5baa394e34c8..3afd87f8c0b1 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -437,46 +437,6 @@ static inline int khugepaged_test_exit(struct mm_struct *mm)
> >       return atomic_read(&mm->mm_users) == 0;
> >  }
> >
> > -bool hugepage_vma_check(struct vm_area_struct *vma,
> > -                     unsigned long vm_flags)
> > -{
> > -     if (!transhuge_vma_enabled(vma, vm_flags))
> > -             return false;
> > -
> > -     if (vm_flags & VM_NO_KHUGEPAGED)
> > -             return false;
> > -
> > -     /* Don't run khugepaged against DAX vma */
> > -     if (vma_is_dax(vma))
> > -             return false;
> > -
> > -     /* Check alignment for file vma and size for both file and anon vma */
> > -     if (!transhuge_vma_suitable(vma, (vma->vm_end - HPAGE_PMD_SIZE)))
> > -             return false;
> > -
> > -     /* Enabled via shmem mount options or sysfs settings. */
> > -     if (shmem_file(vma->vm_file))
> > -             return shmem_huge_enabled(vma);
> > -
> > -     if (!khugepaged_enabled())
> > -             return false;
> > -
> > -     /* THP settings require madvise. */
> > -     if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always())
> > -             return false;
> > -
> > -     /* Only regular file is valid */
> > -     if (file_thp_enabled(vma))
> > -             return true;
> > -
> > -     if (!vma->anon_vma || !vma_is_anonymous(vma))
> > -             return false;
> > -     if (vma_is_temporary_stack(vma))
> > -             return false;
> > -
> > -     return true;
> > -}
> > -
> >  void __khugepaged_enter(struct mm_struct *mm)
> >  {
> >       struct mm_slot *mm_slot;
> > @@ -513,7 +473,7 @@ void khugepaged_enter_vma(struct vm_area_struct *vma,
> >  {
> >       if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
> >           khugepaged_enabled()) {
> > -             if (hugepage_vma_check(vma, vm_flags))
> > +             if (hugepage_vma_check(vma, vm_flags, false))
> >                       __khugepaged_enter(vma->vm_mm);
> >       }
> >  }
> > @@ -958,7 +918,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
> >
> >       if (!transhuge_vma_suitable(vma, address))
> >               return SCAN_ADDRESS_RANGE;
> > -     if (!hugepage_vma_check(vma, vma->vm_flags))
> > +     if (!hugepage_vma_check(vma, vma->vm_flags, false))
> >               return SCAN_VMA_CHECK;
> >       /*
> >        * Anon VMA expected, the address may be unmapped then
> > @@ -1448,7 +1408,7 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr)
> >        * the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check()
> >        * will not fail the vma for missing VM_HUGEPAGE
> >        */
> > -     if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE))
> > +     if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE, false))
> >               return;
> >
> >       /* Keep pmd pgtable for uffd-wp; see comment in retract_page_tables() */
> > @@ -2143,7 +2103,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
> >                       progress++;
> >                       break;
> >               }
> > -             if (!hugepage_vma_check(vma, vma->vm_flags)) {
> > +             if (!hugepage_vma_check(vma, vma->vm_flags, false)) {
> >  skip:
> >                       progress++;
> >                       continue;
> > --
> > 2.26.3
> >