On 19 Jun 2020, at 17:56, Ralph Campbell wrote:
> Transparent huge page allocation policy is controlled by several sysfs
> variables. Rather than expose these to each device driver that needs to
> allocate THPs, provide a helper function.
>
> Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
> ---
> include/linux/gfp.h | 10 ++++++++++
> mm/huge_memory.c | 16 ++++++++++++++++
> 2 files changed, 26 insertions(+)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 67a0774e080b..1c7d968a27d3 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -562,6 +562,16 @@ extern struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
> alloc_pages_vma(gfp_mask, 0, vma, addr, numa_node_id(), false)
> #define alloc_page_vma_node(gfp_mask, vma, addr, node) \
> alloc_pages_vma(gfp_mask, 0, vma, addr, node, false)
> +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
> +extern struct page *alloc_transhugepage(struct vm_area_struct *vma,
> + unsigned long addr);
> +#else
> +static inline struct page *alloc_transhugepage(struct vm_area_struct *vma,
> + unsigned long addr)
> +{
> + return NULL;
> +}
> +#endif
>
> extern unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order);
> extern unsigned long get_zeroed_page(gfp_t gfp_mask);
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 25d95f7b1e98..f749633ed350 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -775,6 +775,22 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
> return __do_huge_pmd_anonymous_page(vmf, page, gfp);
> }
>
> +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
> +struct page *alloc_transhugepage(struct vm_area_struct *vma,
> + unsigned long haddr)
> +{
> + gfp_t gfp;
> + struct page *page;
> +
> + gfp = alloc_hugepage_direct_gfpmask(vma);
> + page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
> + if (page)
> + prep_transhuge_page(page);
> + return page;
> +}
> +EXPORT_SYMBOL_GPL(alloc_transhugepage);
> +#endif
> +
> static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
> pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
> pgtable_t pgtable)
> --
> 2.20.1
Why use CONFIG_ARCH_ENABLE_THP_MIGRATION to guard THP allocator helper?
Shouldn’t CONFIG_TRANSPARENT_HUGEPAGE be used? Also the helper still allocates
a THP even if transparent_hugepage_enabled(vma) is false, which is wrong, right?
--
Best Regards,
Yan Zi
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