diff mbox series

[v2,16/46] hugetlb: make default arch_make_huge_pte understand small mappings

Message ID 20230218002819.1486479-17-jthoughton@google.com
State New
Headers
Series hugetlb: introduce HugeTLB high-granularity mapping |

Commit Message

James Houghton Feb. 18, 2023, 12:27 a.m. UTC 
  This is a simple change: don't create a "huge" PTE if we are making a
regular, PAGE_SIZE PTE. All architectures that want to implement HGM
likely need to be changed in a similar way if they implement their own
version of arch_make_huge_pte.

Signed-off-by: James Houghton <jthoughton@google.com>

Comments

Mina Almasry Feb. 22, 2023, 9:17 p.m. UTC | #1 
On Fri, Feb 17, 2023 at 4:28 PM James Houghton <jthoughton@google.com> wrote:
>
> This is a simple change: don't create a "huge" PTE if we are making a
> regular, PAGE_SIZE PTE. All architectures that want to implement HGM
> likely need to be changed in a similar way if they implement their own
> version of arch_make_huge_pte.
>
> Signed-off-by: James Houghton <jthoughton@google.com>
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 726d581158b1..b767b6889dea 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -899,7 +899,7 @@ static inline void arch_clear_hugepage_flags(struct page *page) { }
>  static inline pte_t arch_make_huge_pte(pte_t entry, unsigned int shift,
>                                        vm_flags_t flags)
>  {
> -       return pte_mkhuge(entry);
> +       return shift > PAGE_SHIFT ? pte_mkhuge(entry) : entry;
>  }
>  #endif
>

How are contig_pte's handled here? Will shift show that it's actually
a contig_pte and not just PAGE_SHIFT? Or is that arm64 specific so it
exists only in the arm64 version of this function? Do we need to worry
about it here?

> --
> 2.39.2.637.g21b0678d19-goog
>
James Houghton Feb. 22, 2023, 10:52 p.m. UTC | #2 
On Wed, Feb 22, 2023 at 1:18 PM Mina Almasry <almasrymina@google.com> wrote:
>
> On Fri, Feb 17, 2023 at 4:28 PM James Houghton <jthoughton@google.com> wrote:
> >
> > This is a simple change: don't create a "huge" PTE if we are making a
> > regular, PAGE_SIZE PTE. All architectures that want to implement HGM
> > likely need to be changed in a similar way if they implement their own
> > version of arch_make_huge_pte.
> >
> > Signed-off-by: James Houghton <jthoughton@google.com>
> >
> > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> > index 726d581158b1..b767b6889dea 100644
> > --- a/include/linux/hugetlb.h
> > +++ b/include/linux/hugetlb.h
> > @@ -899,7 +899,7 @@ static inline void arch_clear_hugepage_flags(struct page *page) { }
> >  static inline pte_t arch_make_huge_pte(pte_t entry, unsigned int shift,
> >                                        vm_flags_t flags)
> >  {
> > -       return pte_mkhuge(entry);
> > +       return shift > PAGE_SHIFT ? pte_mkhuge(entry) : entry;
> >  }
> >  #endif
> >
>
> How are contig_pte's handled here? Will shift show that it's actually
> a contig_pte and not just PAGE_SHIFT? Or is that arm64 specific so it
> exists only in the arm64 version of this function? Do we need to worry
> about it here?

arm64 implements its own version of arch_make_huge_pte, and 'shift'
does indeed indicate (to arm64) if the PTE is contiguous or not (like
it will be CONT_PTE_SHIFT, for example).
Mike Kravetz Feb. 28, 2023, 11:02 p.m. UTC | #3 
On 02/18/23 00:27, James Houghton wrote:
> This is a simple change: don't create a "huge" PTE if we are making a
> regular, PAGE_SIZE PTE. All architectures that want to implement HGM
> likely need to be changed in a similar way if they implement their own
> version of arch_make_huge_pte.
> 
> Signed-off-by: James Houghton <jthoughton@google.com>
> 
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 726d581158b1..b767b6889dea 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h

Thanks,
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
diff mbox series

Patch

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 726d581158b1..b767b6889dea 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -899,7 +899,7 @@  static inline void arch_clear_hugepage_flags(struct page *page) { }
 static inline pte_t arch_make_huge_pte(pte_t entry, unsigned int shift,
 				       vm_flags_t flags)
 {
-	return pte_mkhuge(entry);
+	return shift > PAGE_SHIFT ? pte_mkhuge(entry) : entry;
 }
 #endif