Messages in this thread | | | Date | Mon, 21 Aug 2017 18:23:09 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCHv4 08/14] x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable |
| |
On Thu, Aug 17, 2017 at 01:10:05PM +0200, Ingo Molnar wrote: > > * Kirill A. Shutemov <kirill@shutemov.name> wrote: > > > 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%. > > Please add this info to one of the changelogs. > > BTW., some of that might be won back via the later optimizations, right?
Sorry, but no. Just chacked. Introducing alternatives increases .text segment size by about 4k.
-- Kirill A. Shutemov
| |