From: Dan Williams <dan.j.williams@xxxxxxxxx> Subject: mm: always enable thp for dax mappings The madvise policy for transparent huge pages is meant to avoid unwanted allocations of transparent huge pages. It allows a policy of disabling the extra memory pressure and effort to arrange for a huge page when it is not needed. DAX by definition never incurs this overhead since it is statically allocated. The policy choice makes even less sense for device-dax which tries to guarantee a given tlb-fault size. Specifically, the following setting: echo never > /sys/kernel/mm/transparent_hugepage/enabled ...violates that guarantee and silently disables all device-dax instances with a 2M or 1G alignment. So, let's avoid that non-obvious side effect by force enabling thp for dax mappings in all cases. It is worth noting that the reason this uses vma_is_dax(), and the resulting header include changes, is that previous attempts to add a VM_DAX flag were NAKd. Link: http://lkml.kernel.org/r/149739531127.20686.15813586620597484283.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> Reviewed-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/dax.h | 5 ----- include/linux/fs.h | 6 ++++++ include/linux/huge_mm.h | 5 +++++ 3 files changed, 11 insertions(+), 5 deletions(-) diff -puN include/linux/dax.h~mm-always-enable-thp-for-dax-mappings include/linux/dax.h --- a/include/linux/dax.h~mm-always-enable-thp-for-dax-mappings +++ a/include/linux/dax.h @@ -154,11 +154,6 @@ static inline unsigned int dax_radix_ord #endif int dax_pfn_mkwrite(struct vm_fault *vmf); -static inline bool vma_is_dax(struct vm_area_struct *vma) -{ - return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host); -} - static inline bool dax_mapping(struct address_space *mapping) { return mapping->host && IS_DAX(mapping->host); diff -puN include/linux/fs.h~mm-always-enable-thp-for-dax-mappings include/linux/fs.h --- a/include/linux/fs.h~mm-always-enable-thp-for-dax-mappings +++ a/include/linux/fs.h @@ -18,6 +18,7 @@ #include <linux/bug.h> #include <linux/mutex.h> #include <linux/rwsem.h> +#include <linux/mm_types.h> #include <linux/capability.h> #include <linux/semaphore.h> #include <linux/fcntl.h> @@ -3127,6 +3128,11 @@ static inline bool io_is_direct(struct f return (filp->f_flags & O_DIRECT) || IS_DAX(filp->f_mapping->host); } +static inline bool vma_is_dax(struct vm_area_struct *vma) +{ + return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host); +} + static inline int iocb_flags(struct file *file) { int res = 0; diff -puN include/linux/huge_mm.h~mm-always-enable-thp-for-dax-mappings include/linux/huge_mm.h --- a/include/linux/huge_mm.h~mm-always-enable-thp-for-dax-mappings +++ a/include/linux/huge_mm.h @@ -3,6 +3,8 @@ #include <linux/sched/coredump.h> +#include <linux/fs.h> /* only for vma_is_dax() */ + extern int do_huge_pmd_anonymous_page(struct vm_fault *vmf); extern int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, @@ -103,6 +105,9 @@ static inline bool transparent_hugepage_ if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_FLAG)) return true; + if (vma_is_dax(vma)) + return true; + if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)) return !!(vma->vm_flags & VM_HUGEPAGE); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
