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| author |   Dan Williams <dan.j.williams@intel.com> | 2017-07-10 15:48:25 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2017-07-10 16:32:31 -0700 |
| commit | baabda261424517110ea98c6651f632ebf2561e3 (patch) | |
| tree | cf02e6ec756e3c090ac7bfe463dc237b7b9e10ab /include/linux/huge_mm.h | |
| parent | mm: improve readability of transparent_hugepage_enabled() (diff) | |
| download | wireguard-linux-baabda261424517110ea98c6651f632ebf2561e3.tar.xz wireguard-linux-baabda261424517110ea98c6651f632ebf2561e3.zip | |
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@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/huge_mm.h')
| -rw-r--r-- | include/linux/huge_mm.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index f4239d3c9c73..ee696347f928 100644 --- a/include/linux/huge_mm.h +++ b/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_enabled(struct vm_area_struct *vma) 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); |