On 6/21/20 5:15 PM, Zi Yan wrote:
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) -- 2.20.1Why 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
Oops, I'm not sure why I thought that was needed. The whole file is only compiled if CONFIG_TRANSPARENT_HUGEPAGE is defined and the calls to alloc_hugepage_vma() and alloc_hugepage_direct_gfpmask() are unprotected just above this in do_huge_pmd_anonymous_page(). I'll fix that in v2. The helper is intended to be called by a device driver to allocate a THP when migrating device private memory back to system memory. The THP should never be migrated to device private memory in the first place if transparent_hugepage_enabled(vma) is false. I suppose I could add a if (WARN_ON_ONCE()) return NULL as a sanity check. The real checks are in migrate_vma_setup() and migrate_vma_pages().
