On Sat, May 04, 2013 at 12:19:03AM +0530, Aneesh Kumar K.V wrote:

David Gibson [off-list ref] writes:

quoted

On Mon, Apr 29, 2013 at 01:21:49AM +0530, Aneesh Kumar K.V wrote:

quoted

From: "Aneesh Kumar K.V" <redacted>

We enable only if the we support 16MB page size.

Signed-off-by: Aneesh Kumar K.V <redacted>
---
 arch/powerpc/include/asm/pgtable-ppc64.h |  3 +--
 arch/powerpc/mm/pgtable_64.c             | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/pgtable-ppc64.h b/arch/powerpc/include/asm/pgtable-ppc64.h
index 97fc839..d65534b 100644
--- a/arch/powerpc/include/asm/pgtable-ppc64.h
+++ b/arch/powerpc/include/asm/pgtable-ppc64.h

@@ -426,8 +426,7 @@ static inline unsigned long pmd_pfn(pmd_t pmd)
 	return pmd_val(pmd) >> PTE_RPN_SHIFT;
 }
 
-/* We will enable it in the last patch */
-#define has_transparent_hugepage() 0
+extern int has_transparent_hugepage(void);
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 static inline int pmd_young(pmd_t pmd)

diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index 54216c1..b742d6f 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c

@@ -754,6 +754,34 @@ void update_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long addr,
 	return;
 }
 
+int has_transparent_hugepage(void)
+{
+	if (!mmu_has_feature(MMU_FTR_16M_PAGE))
+		return 0;
+	/*
+	 * We support THP only if HPAGE_SHIFT is 16MB.
+	 */
+	if (!HPAGE_SHIFT || (HPAGE_SHIFT != mmu_psize_defs[MMU_PAGE_16M].shift))
+		return 0;

Again, THP should not be dependent on the value of HPAGE_SHIFT.  Just
checking that mmu_psize_defsz[MMU_PAGE_16M].shift == 24 should be
sufficient (i.e. that 16M hugepages are supported).

done

+	/*
+	 * We support THP only if PMD_SIZE is 16MB.
+	 */
+	if (mmu_psize_defs[MMU_PAGE_16M].shift != PMD_SHIFT)
+		return 0;
+	/*

Much better.

quoted

quoted

+	/*
+	 * We need to make sure that we support 16MB hugepage in a segement
+	 * with base page size 64K or 4K. We only enable THP with a PAGE_SIZE
+	 * of 64K.
+	 */
+	/*
+	 * If we have 64K HPTE, we will be using that by default
+	 */
+	if (mmu_psize_defs[MMU_PAGE_64K].shift &&
+	    (mmu_psize_defs[MMU_PAGE_64K].penc[MMU_PAGE_16M] == -1))
+		return 0;
+	/*
+	 * Ok we only have 4K HPTE
+	 */
+	if (mmu_psize_defs[MMU_PAGE_4K].penc[MMU_PAGE_16M] == -1)
+		return 0;

Except you don't actually support THP on 4K base page size yet.

That is 64K linux page size and 4K HPTE . We do support that.

Good point, sorry.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson