[PATCH V2] powerpc/mm/hugetlb: initialize the pagetable cache correctly for hugetlb

[PATCH V2] powerpc/mm/hugetlb: initialize the pagetable cache correctly for hugetlb

[Aneesh Kumar K.V]

With 64k page size, we have hugetlb pte entries at the pmd and pud level for
book3s64. We don't need to create a separate page table cache for that. With 4k
we need to make sure hugepd page table cache for 16M is placed at PUD level
and 16G at the PGD level.

Simplify all these by not using HUGEPD_PD_SHIFT which is confusing for book3s64.

Without this patch, with 64k page size we create pagetable caches with shift
value 10 and 7 which are not used at all.

Fixes:419df06eea5bfa81("powerpc: Reduce the PTE_INDEX_SIZE")

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/powerpc/mm/hugetlbpage.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 876da2bc1796..3b509b268030 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -122,9 +122,6 @@ static int __hugepte_alloc(struct mm_struct *mm, hugepd_t *hpdp,
 #if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_8xx)
 #define HUGEPD_PGD_SHIFT PGDIR_SHIFT
 #define HUGEPD_PUD_SHIFT PUD_SHIFT
-#else
-#define HUGEPD_PGD_SHIFT PUD_SHIFT
-#define HUGEPD_PUD_SHIFT PMD_SHIFT
 #endif
 
 /*
@@ -669,12 +666,24 @@ static int __init hugetlbpage_init(void)
 		if (add_huge_page_size(1ULL << shift) < 0)
 			continue;
 
+
+#ifdef CONFIG_PPC_BOOK3S_64
+		if (shift > PGDIR_SHIFT)
+			BUG();
+		else if (shift > PUD_SHIFT)
+			pdshift = PGDIR_SHIFT;
+		else if (shift > PMD_SHIFT)
+			pdshift = PUD_SHIFT;
+		else
+			pdshift = PMD_SHIFT;
+#else
 		if (shift < HUGEPD_PUD_SHIFT)
 			pdshift = PMD_SHIFT;
 		else if (shift < HUGEPD_PGD_SHIFT)
 			pdshift = PUD_SHIFT;
 		else
 			pdshift = PGDIR_SHIFT;
+#endif
 		/*
 		 * if we have pdshift and shift value same, we don't
 		 * use pgt cache for hugepd.
-- 
2.14.3

Re: [PATCH V2] powerpc/mm/hugetlb: initialize the pagetable cache correctly for hugetlb

[Michael Ellerman]

"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> writes:
> With 64k page size, we have hugetlb pte entries at the pmd and pud level for
> book3s64. We don't need to create a separate page table cache for that. With 4k
> we need to make sure hugepd page table cache for 16M is placed at PUD level
> and 16G at the PGD level.
>
> Simplify all these by not using HUGEPD_PD_SHIFT which is confusing for book3s64.
>
> Without this patch, with 64k page size we create pagetable caches with shift
> value 10 and 7 which are not used at all.
>
> Fixes:419df06eea5bfa81("powerpc: Reduce the PTE_INDEX_SIZE")

That's:

  Fixes: 419df06eea5b ("powerpc: Reduce the PTE_INDEX_SIZE")

In ~/.gitconfig:

[pretty]
	fixes = Fixes: %h (\"%s\")


> diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
> index 876da2bc1796..3b509b268030 100644
> --- a/arch/powerpc/mm/hugetlbpage.c
> +++ b/arch/powerpc/mm/hugetlbpage.c
> @@ -669,12 +666,24 @@ static int __init hugetlbpage_init(void)
>  		if (add_huge_page_size(1ULL << shift) < 0)
>  			continue;
>  
> +
> +#ifdef CONFIG_PPC_BOOK3S_64
> +		if (shift > PGDIR_SHIFT)
> +			BUG();

Can we not add BUG()s for things that aren't utterly fatal.

In this case I think we could move this whole block above
add_huge_page_size() above, and then instead of BUG() we could just
WARN() and continue?

> +		else if (shift > PUD_SHIFT)
> +			pdshift = PGDIR_SHIFT;
> +		else if (shift > PMD_SHIFT)
> +			pdshift = PUD_SHIFT;
> +		else
> +			pdshift = PMD_SHIFT;
> +#else
>  		if (shift < HUGEPD_PUD_SHIFT)
>  			pdshift = PMD_SHIFT;
>  		else if (shift < HUGEPD_PGD_SHIFT)
>  			pdshift = PUD_SHIFT;
>  		else
>  			pdshift = PGDIR_SHIFT;
> +#endif
>  		/*
>  		 * if we have pdshift and shift value same, we don't
>  		 * use pgt cache for hugepd.

cheers