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    SubjectRe: [PATCHv4 08/14] x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable
    On Thu, Aug 17, 2017 at 11:00:38AM +0200, Ingo Molnar wrote:
    >
    > * Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote:
    >
    > > For boot-time switching between 4- and 5-level paging we need to be able
    > > to fold p4d page table level at runtime. It requires variable
    > > PGDIR_SHIFT and PTRS_PER_P4D.
    > >
    > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    > > ---
    > > arch/x86/boot/compressed/kaslr.c | 5 +++++
    > > arch/x86/include/asm/pgtable_32.h | 2 ++
    > > arch/x86/include/asm/pgtable_32_types.h | 2 ++
    > > arch/x86/include/asm/pgtable_64_types.h | 15 +++++++++++++--
    > > arch/x86/kernel/head64.c | 9 ++++++++-
    > > arch/x86/mm/dump_pagetables.c | 12 +++++-------
    > > arch/x86/mm/init_64.c | 2 +-
    > > arch/x86/mm/kasan_init_64.c | 2 +-
    > > arch/x86/platform/efi/efi_64.c | 4 ++--
    > > include/asm-generic/5level-fixup.h | 1 +
    > > include/asm-generic/pgtable-nop4d.h | 1 +
    > > include/linux/kasan.h | 2 +-
    > > mm/kasan/kasan_init.c | 2 +-
    > > 13 files changed, 43 insertions(+), 16 deletions(-)
    >
    > So I'm wondering what the code generation effect of this is - what's the
    > before/after vmlinux size?
    >
    > My guess is that the effect should be very small, as these constants are not
    > widely used - but I'm only guessing and could be wrong.

    This change increase vmlinux size for defconfig + X86_5LEVEL=y by ~4k or
    0.01%.

    --
    Kirill A. Shutemov

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